The twenty one startups from Y Combinator’s summer session are presenting their ideas and creations to investors in Boston this afternoon. Below are descriptions of the nine startups we haven’t covered and who don’t wish to remain in stealth mode any longer. See our prior coverage of Posterous, Anyvite, ididwork, Popcuts, and Slinkset – all of which are part of this batch and have launched already.

TicketStumbler

TicketStumbler can be described as Kayak for sports tickets. It aggregates tickets from sites like StubHub and RazorGator, making them searchable by keyword and allowing for the filtering of results by maximum price, quantity available, provider, etc. The site is live, fast, and gets extra points for not spelling “stumbler” without the “e”.

People and Pages

While yet to launch, the founders of People and Pages describe their service as “a better Google Groups”, although the screenshots show that it’s part WYSIWYG website creation tool as well, making it competitive with Google Sites, Weebly (also a Y Combinator startup), and others. Group organizers can use People and Pages to manage email lists and publish to the web in one place.

MeetCast

MeetCast is a WebEx and GoToMeeting competitor (yes, another one) that is marketing itself on ease of use (no downloads) and playback (all conferences are saved and indexed for later viewing). The founders draw comparisons to Tokbox for its simplicity.

CO2Stats

For a flat monthly fee, CO2Stats will measure the overall electricity usage of websites and then automatically buy renewable energy certificates for them to offset their effective emissions. Founded by academics from Harvard and Yale, CO2Stats has already turned a profit by signing up 2,500+ sites in over 25 countries. See our review from earlier today.

Youlicit

Youlicit is a service prepping for relaunch that will generate Mahalo-like search guides by scouring the web for user generated content and compiling it into topics algorithmically instead of relying on human editors. These search guides themselves are intended to show up highly in the results of more traditional search engines like Google.

Job Alchemist

Job Alchemist is the parent company of two online services: Startuply, a job site for tech startups that we covered last month, and a new job affiliate network called JobSyndicate that launches today. Publishers can place JobSyndicate’s widgets on their sites and earn half the bounty set by employers when visitors click through and get hired.

Frogmetrics

Frogmetrics isn’t a pure web venture: the company wants to place touch screens in restaurants, stores, and other brick and mortar establishments that can be used to collect customer feedback on the spot. The devices ask customers a few questions at the point of sale about their experience and can collect contact information about customers to generate leads. The information gathered across physical locations is aggregated and analyzed for trends and other statistics.

Snipd

Snipd appears to be another web annotation service, one that allows users to “snip” page content such as images, videos, and text to share them with others and save for later. These snips are also used to generate so-called heat maps of pages that help users find the best content on a page. The service has yet to launch.

BackType

BackType is a search engine for comments that crawls the internet for blogs and indexes their user generated content regardless of the platform (WordPress, Moveable Type, etc). These comments are not only keyword searchable but can be followed by author, allowing you to keep track of what your friends are saying online.

Three years ago, Paul Graham and his Y Combinator incubator funded Reddit, a social news site that has grown to over 2.5 million unique visitors a month. Reddit has never been able to match the success of Digg, its closest competitor, but in 2006 it got its payday after being acquired by Condé Nast/Wired for an undisclosed amount.

Now, it seems that Y Combinator is hoping that lightning will strike twice. Its latest startup, Slinkset, is looking to offer a “hosted Reddit” solution, allowing users to create their own social news sites with as little technical knowhow as possible. You can see a hosted version of the site that has been created for TechCrunch readers here.

At first glance, Slinkset looks like little more than a Reddit clone. Users can vote news stories Up or Down, with the most popular stories rising to the top of the page. The big difference here is that unlike Digg and Reddit, Slinkset isn’t looking to become a destination site. Instead, it’s offering users the chance to create their own branded “Reddits” with no coding necessary. For the time being Slinkset is offering its hosting service free of charge, with plans to introduce a fixed fee in the future.

Unfortunately, despite its aspirations to let users to create no-hassle branded pages, Slinkset’s customization options are pretty limited. Site admins can easily swap the color schemes, adjust fonts, and add a logo, but that’s about it. In the future the site hopes to integrate drag-and-drop widgets and ad placement, but with a company that currently consists of only two co-founders, these are probably a ways off.

So is Slinkset really necessary? You can already create your own hosted Reddit through Reddit itself (albeit with limited customizability). Mixx, another competitor in this space, also features a similar hosted offering.

And the site’s launch comes less than a month after Reddit went open-source, allowing developers to create their own, fully tweakable, Reddit clones (you can see our version, Tech News, here). Slinkset co-founder Brett Gibson says that while the release of Reddit’s source code will help skilled programmers create their own social news site, it won’t do any good for the legions of bloggers and small-time sites that don’t know how to implement it, which is where he hopes Slinkset comes in. This may be the case, but unless Slinkset can improve on its customization features, it will have a hard time separating itself from its well-established competitors.