As if we needed yet another URL shortening service, TweetMeme is today debuting ReTwt.me in an effort to make that particular saturated field even more so. And it’s not like it does anything special in comparison with the plethora of similar services out there.

It shrinks longer links in order to make them more tweetable (and retweetable), it gives you some options to share links from its main website, throws in some analytics so you can see just how few people actually click those links you’re spreading and comes with an API.

The only slight advantage it could have over competitors like TinyURL and bit.ly is a tight integration with the TweetMeme service / button, but they won’t be exploiting that connection and keep on supporting the URL shortening services as they were before (which is obviously the right thing to do).

When it comes to shortening links, the brevity of the URL is not the only factor you should consider. Speed and reliability are also important. After all, the main purpose of URL shortening services such as bit.ly and TinyURL are to redirect you back to the original (long) link someone shortened in the first place. You want the redirect to be fast and reliable.

The rise of Twitter and its character constraints has made URL shortening services popular. But which one is the best? Royal Pingdom decided to conduct a test over the past 30 days to put nine of URL shortening services through the paces. Overall, Ow.ly and Bit.ly came out on top, while Tr.im came in dead last (no wonder nobody would buy it).

Pingdom tested two things: the average time it took each service to load a page (overhead) and its uptime

Sharing links on Twitter can be quite a pain when you need to input a web address that consumes most of the space you have at your disposal for your micro-message. The startup realized that quickly and automatically started shortening long URLs to make its users save on space for their 140-character updates.

To get this implemented, Twitter went with TinyURL, a service that shortens URLs down signficantly (but not extremely) and at the time had been around for years already. It never gave a reason for this choice, but it did provide TinyURL with a lot of exposure and a lot of extra traffic.

Those days are over. Apparently, Twitter has silently replaced TinyURL as its default URL shortening service with bit.ly.

URL shortening services are a dime a dozen, and despite wishes for them to vanish (with good reason) they’re here to stay and more popular than ever given the abundance of social services that thrive on short messages and links. TinyURL and bit.ly appear to be the more popular of the bunch, but we’re seeing other services use their own custom URL shortening services at an increasing rate. To name but a few, Digg uses its top domain for the DiggBar and associated links, Posterous uses post.ly to trim down links when they distribute them to other networks and Twitter toolbox HootSuite uses ow.ly.

Update: shame on me for forgetting that TechCrunch also has its ‘own’ short URL (tcrn.ch), which you can view under every post and which we use for our Twitter account. We use awe.sm for this.

The latest startup to add a URL shortening feature to its service is UnHub, and we’re also taking a look at the new Lnk.by.

One of the most viral activities on the Web is sharing links. It is fast and easy, and a good way to communicate ideas. What started out as something people did via e-mail and bookmark-sharing services like Delicious, is now moving to Facebook, Twitter, and other social broadcasting services. It is just so much more efficient to share a link once with all your friends and followers than to send it to each one individually.

Twitter is especially suited to sharing quick links, but its 140-character limit has perhaps done more than anything else to propel forward the use of URL shorteners. These take long URLs and turn them into shorter ones that usually redirect people back to the original. There are more than a dozen such services, including TinyURL, bit.ly, Snurl, tr.im, is.gd, and the new Diggbar. Nobody really likes them, but they are a necessary evil. How else are you going to share links on Twitter without having the URL take up half the message?

It may be more complicated than that, however. Joshua Schachter, the founder of Delicious, thinks they are downright evil.

In a world where everything is being jammed into 140 characters or less, shorter is better. That goes double (or is it half?) for lengthy URLs. So-called URL shortening services are increasingly becoming indispensable to anyone who uses Twitter. It is the only practical way to share links on the service.

Today, one of these URL shortening services, bit.ly, raised $2 million, sparking the question: How much are these things actually worth? Nobody really knows.

But here is some fun math. Assuming bit.ly sold 20 percent of its shares to its new investors (the O’Reilly Alpha Tech Fund, Mitch Kapor, and Howard Lindzon), that would imply an $8 million pre-money valuation ($10 million post-money). Its market share of shortened links, as calculated by Tweetmeme, is only 13 percent. The biggest URL shortner out there is actually TinyURL, which commands a 75 percent share. So by that metric, if bit.ly is worth $8 million, TinyURL should be worth at least $46 million (8/13 X 75 = 46.15). Yes, I am making up these numbers, just like the investors do.

But wait. Bit.ly seems to be shooting up like a rocket, while TinyURL may have plateaued. Why is bit.ly growing so much faster? One big reason is because it creates even shorter URLs than TinyURL does by about five characters (http://bit.ly/ versus http://tinyurl.com/). Don’t laugh. Every character counts. Bit.ly also offers better analytics and tracking tools on the backend.

A super-secret Digg toolbar has been spotted in the wild. We tracked down a beta tester who gave us the skinny on its features. The toolbar lets you Digg or Bury the page you are on, and shows how many Diggs it has already received. There are also links to show related pages, as well as more pages from the same source voted highly by the Digg community or marked as up and coming.

Then there is the “Random” button which works like StumbleUpon. It takes you to a randomly-generated page based on your past input and overall Digg voting. By the prominence of this button, it appears that is a feature Digg will be trying to highlight. Users can also share the page via Facebook, Twitter, or email via icons at the top. A drawer slides down to expose additional functionality.

Now, here where it gets interesting. For each page, the toolbar creates a shortened URL similar to TinyURL or bit.ly that starts instead with http://digg.com/. . . followed by a six-character code such as “http://digg.com/d1gVha.” When you share a page via Twitter or Facebook, it is that shortened URL which is used. And in fact, for the beta testers, the toolbar can be wrapped around any page simply by sticking “http://digg.com/” in front of any URL, which then gets converted into a shortened version.

TinyURL is the place to go if you have a long URL that you want to cut down for friends, but if you’re looking for a way to easily send Google search results to them without picking a specific page, Look.fo lets you send them an exact link to your query in a simple style: look.fo/your search query.

I had the opportunity to try out Look.fo and it works as advertised. The page’s design is simple and contains a search box that lets you input your query. Once you do, a vanity URL is created so you can copy it and send it along. You can also search on the Look.fo site by inputting your query, which then brings you to the Google search results page.

I tried Look.fo out with something easy like “TechCrunch” and the site performed well. It quickly formed the URL (http://look.fo/techcrunch) and the Google search results it returned were accurate enough for me to justify sending that to someone who wants to know more about TechCrunch.