Twice a year, Y Combinator holds special events called Demo Day, when its most recent batch of startups present to a packed room full of top investors. It’s the grand finale of the program, where entrepreneurs have a few minutes to show off what they’ve built in the hopes of raising a seed round to help their companies stay afloat for at least a few more months (and hopefully much longer).

Of course, Demo Day is a bit different from what it was a year or two ago. The spectre of a $0 bank account is further off, as Y Combinator companies are now being offered $150,000 in convertible debt by Start Fund, the fund created by Yuri Milner and Ron Conway’s SV Angel. And there are now more companies than ever — 43 companies presented during Demo Day this afternoon, which means they’re each given a bit less time.

But the spirit is still the same. It’s a whirlwind introduction to some of the most promising tech startups around, and investors are so eager to attend that Y Combinator has had to start offering two Demo Days per session. The investors at today’s session (which is generally more desirable than day two) had something special in common: YC cofounder Paul Graham announced that all investors in attendance had previously invested in a Y Combinator company.

We’ve already covered many of the companies that presented today (and most of the others were off the record). Here’s a handy list of links to our past coverage.

• Comprehend Systems Wants To Make Data Analysis Less Of A Pain
• Convore Wants To Be The Easiest Group Communication App Yet
• YC-Funded HelloFax: Sign And Send Faxes From Your Browser, Without The Hassle
• YC-Backed Tutorspree Is An Airbnb For Tutoring
• YC-Funded Earbits Brings A Twist To Music Startups: Online Radio That Lets Bands Pay For Playtime
• YC-Backed TellFi Is Like “Google Voice” For Companies
• Beetailer Helps Online Retailers Set Up Shop On Facebook
• FitFu Wants To Get You Exercising At Your Desk, And Everywhere Else
• YouGotListings Offers A Broker-Tested Rental Listing Management Software
• DrChrono Makes The iPad A Doctor’s Best Friend In The Exam Room
• Custora Helps Online Businesses Improve Customer Retention
• Taskforce Helps You Organize Your Inbox and Become a Taskmaster
• Meet The People You Follow On Twitter With YC-Funded Conference Directory Lanyrd
• SwipeGood Raises $500K From Michael Birch And Others To Allow You To Donate With Each Purchase
• GiftRocket Lets You Send Gifts That Can Be Redeemed At Specific Locations
• Noteleaf Takes Mobile Meeting Notifications To A Whole New Level
• Grubwithus — We haven’t previously covered them, but they have a compelling service. Restaurants can sign up to offer ‘meals’, where there are a fixed number of seats available for the price of a meal (around $25). Other people — probably strangers — will take up the other spots, so when you meet for that meal you have a good chance of meeting new friends, possible dating prospects, or work connections.
• YC-Funded AppHarbor: A Heroku For .NET, Or “Azure Done Right”
• Youngest Y Combinator Founders Launch MinoMonsters, The Pokemon Of Social Games
• Curebit — a service that makes it easy to create referral marketing campaigns, like the one Dropbox has very effectively leveraged to gain loads of new users.
• Moki.TV Is The Ultimate, Personalized Guide To What’s Streaming On The Web
• Sendoid: Finally, Sharing Big Files Isn’t A Huge Pain
• YC-Backed Like.fm Is A Social Network For Tracking Songs
• Five Stars — Looking to offer businesses a ‘universal loyalty card’, based on an iPhone application. Sounds similar to PlacePop. The Five Stars founders say this description is misleading — their tagline is “A universal loyalty card for retail businesses. The FiveStars platform is the first link between cash registers and customers’ Facebook and email accounts.”, and rather than focus on an iPhone app, they track users based on their phone numbers. The system runs from business’s Point of Sales machines.

Crunchbase

• Y COMBINATOR

Company: Y Combinator

Website: ycombinator.com

Launch Date: April 1, 2005

Funding: $10.3M

Y Combinator is a venture fund which focuses on seed investments to startup companies. It offers financing as well as business consulting along with other opportunities to 2-4 person companies looking to take an idea to a product. Y Combinator looks for companies with “good” ideas over companies with experience and a business model. The company made its first investments in Summer 2005. Y Combinator selects companies to finance and consult with twice a year. They are located in...

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