Take a step back for a day and look at your idea/application. Did you explain clearly what the idea was? Will it create value for users? How will you get people to adopt it?
Once you've figured out what went wrong, fix it then get on with creating your app. Creating a startup is filled with setbacks, the trick is to keep going.
If you applied on a "Let's see if we can convince Paul to let us come to YC Summer Camp, and maybe we'll be rich this time next year" whim with not a lot of code written...maybe you go back to school and work on other ideas. Try again for Winter with a different idea or more code and a better presentation. Or apply for a job at an existing startup. Some of the WFP guys are hiring (Parakey, Zenter, and a few others) as are the Xobni guys from last years progem--all are wicked smart, have lined up some funding, and would be very helpful to you in your goal of becoming an entrepreneur.
If, on the other hand, you've already written mumble-thousand LoC, and you are within a couple of months of launching, and you really believe in your idea and product, contact some other angels and seed investors. They exist. They aren't as cool as YC, but they have money and they have connections, too. As a last resort, if you're in the wrong city for raising money (anything other than Silicon Valley or Boston), warm up your credit card and give it a go. You can live for three months on a credit card (I've done it several times...I'm on my second company, the first being self-funded and sometimes credit card funded). Obviously, if you've got a family to support the "warm up your credit card" method of funding is right out. Otherwise, just keep your health insurance current, pay your taxes, and live on nothing but ramen and buy nothing between now and launch day.
If your project is too big to launch in that short time, then that's why you were rejected by YC. Winnow it down to the smallest piece that has value and launch. Our project (Virtualmin) was huge (several hundred thousand lines of code, by the time you factor in Webmin and Usermin). But we were already selling product, and figured we were within a couple of months of "finishing" the beta period (we were off by a little bit, as we're still a couple of weeks away from wrapping it up six months later--partly because of the major strategy shifts we made during WFP2007).
One of the implications of choosing this model is that you are limiting your audience and potential market. Is it what users want, NOW? For me this is a need as I have lots of distributed stuff over 10 years but for newer users most of their stuff is in a database, CMS etc.
The market is short sited in this respect. From what I can tell there is a distinct lack of demand. All the top level blogs are platform focused (blogger, wordpress, typepad, mt). These services are so good they don't seem to go down, thus where's the need?
It's a good idea btw, because if you own your own data you become the definitive source. BTW how are you solving the following problems?
- extracting data from services with no API?
- extracting data from services with API's (have to do coding for each service)
- problem of input? Service side input & extraction via API v's Client side input and exporting via API's (if the content is yours)
- How do you visualise the mixing of data?
- Which (key) services do you concentrate on extracting data? Or is it any service?
They key things I got out of thinking making a biz out of this particular idea is that you can get into problems ...
- focus on individual users and miss out any network effects (user foo connects to user bar).
- not creating a new market
- restricting sales by creating a secondary market because users use other services to create and yours (if needed or others) to backup.
So while I'm still building this tool, I'll be looking at areas in this space that I can extract the best/better value (something that people want, faster, savings in time & effort etc) and looking for new ideas associated (and new) while solving this particular problem space for me. Remember Joshua Scharacter took about 4-5 ideas before he refined delicious & created a useful site.
My gut instinct is that manipulating, saving and creating data (in its various forms) is a growing space and finding the edge niche is a potential starting point.
Reference
[0] Ycombinator-StartupSchool, 'Joshua_Schacter, MP3, 28Mb'
http://feeds.feedburner.com/~r/Ycombinator-StartupSchool/~3/106570501/Joshua_Schacter.mp3
You will expose yourself to the risk of theft. On the other hand, ideas are only half the battle.
Good luck.
Think about it as a test. They didn't reject you, its a test. A mission, a quest that will give you 5g, 6000xp, and faction with YCombinator, but remember its an elite quest, bring others.
Do not fail, well fail, but do not fail at failing!