YC Rejected: Please read.
"Why did I get rejected?!??"
I don't know, many of us don't either. Other than your idea possibly being a pile of garbage, none of us here know as to the exact reasons you got rejected. Sure, pg will, but I doubt he'll write up a critique of your app and post it publicly. If you want to know why you were rejected, email someone at yc to see if they're even willing to give you feedback.
"Maybe we should start a YC-rejected group!!!"
Go for it. Honestly, it's a big waste of time. Last year someone created RejectedByYC.com, but that seems to have vanished. I don't really know why you'd want to limit yourself to giving/receiving feedback and support for your project from other YC-rejected companies. The rest of us who got accepted or didn't apply aren't less willing to encourage/support/critique your efforts.
"I got rejected, but I'm moving on!!!"
Awesome, but really, even considering to discontinue a project based on your YC decision is foolish. Sure, the experience is great, you get a little cash to get you off the ground, but if your motivation was that dependent on the outcome of whether you'd be accepted to YC, you need to realize that there are much higher hurdles to be conquered ahead. Plus, we don't need to know you're moving on. Create something, ask for feedback, and we'll care.
"MyStartup (YC reject '09) asking for feedback!!!"
Don't label yourself as a YC reject. I don't know why people do this. I am no more interested in your startup whether accepted or rejected from YC. There are several YC companies I think are crap, and many rejects that I think are awesome. I guess what you're trying to get across by labeling yourself as a YC rejects is "PG thinks we're crap, but I'm out to prove him wrong!" That makes you seem bitter and unable to emotionally settle with your rejection. We are a community of startups and people interested in them and we need not to label ourselves into various camps. There are startups that are accepted into YC, and for those companies, they were each merely granted an opportunity. For every YC accepted company, there's another who has received angel investing sans incubator-type program, and another who has been hooked up with a client that could bring lots of business, and another that just took vc funding. Starting companies is about finding opportunities. And if YC isn't an opportunity that came your way, you have hundreds of other paths to pursue.
I've said this before, but please realize that Digg, Facebook, Twitter, Google, YouTube, Myspace, eBay, Amazon, PayPal, and 99.999% of the most popular and/or highly valued acquired companies didn't go through YC, nor any other YC-like program.
Rejection has a human angle, and refusing to acknowledge that people respond to it in (seemingly) irrational ways doesn't help those who need encouragement, validation, or just knowledge of the fact that they are not alone. How is asking other hackers 'which web framework to use?' any 'better' than asking other YC applicants rejection related questions, given that this is effectively the only public YC forum?
I'm generally a sympathetic person, but I have no interest at all in hearing complete strangers complaining about not getting mentoring and money for their start-up. Most businesses fail very early (including the one I started years back), and most of them don't get these sorts of benefits.
YC is a hell of an opportunity. The advice/mentoring, along with a little bit of cash is big for young ambitious hackers/entrepreneurs/dreamers like us. There is no doubt it gives you an advantage.
At the end of the day, if your startup fails, it won't be due to a rejection from YC or any one specific event. Think about it logically, should one decision/outcome determine if a startup loses? Just being apathetic and letting the world have its way with you, isn't the way to go.
So, go fire up textmate,photoshop,gdocs,or whatever gets you going and keep chugging along. You've taken the time to fill out the application and probably more, so keep going. Post on HN for feedback once the demo is up. The community will actually give you valuable feedback and won't be assholes. You may succeed, you may fail, but I promise you that you will not regret it.
To be a bit of a downer, I think that's why some people are so distraught about getting rejected - sure, some people are going to come out ahead anyway, and some never will no matter how much of a boost they get, but something like YC is a big push for those at the margin. It really could be the difference between success and failure.
my first YC app (for my first company, an online SAT prep which I ran for a few years) was rejected, and their critiques were largely right.
i was accepted 2 years later with a different idea (dropbox).
that said, helpful as it may be, YC is neither a necessary nor sufficient condition for success. it's still up to you to MSPW.
Its quite viable, particularly for small team sizes, and you will learn quite a bit about business, which will serve you in good stead no matter where your career or further ambitions take you.
You'll also note that there are plenty of imitation-worthy businesses out there which were in your shoes once. Basecamp got written as a side project between consulting work. Balsamiq Mockups was a one-man band. I could bore you to death with stories of niche software firms that do pretty well for themselves.
To me, it's just as appropriate to mention as the fact that other companies are "(YC'08)" or whatever.
Your application is what it has accomplished, not what it hasn't. Highlight accordingly.
But teams asking for help/feedback from peers, here, benefit by demonstrating earnestness and tenacity. They don't have to impress by selective disclosure. Acknowledging, without obsessing over, the prior YC rejection at the same time as releasing other positive news heightens the emotional impact of that news.
Founding myths often highlight the many rejections that had to be overcome. For a team that's really on a mission, it's never too early to start sending the message: nothing stops us.
More to the point, I think, is that they benefit by fully disclosing their situation. Disclosing that you are not YC funded (either through rejection or simple disinterest in applying,) is helpful when one is asking for advice.
It might not be something that you want to include in the headline, but it's certainly worth mentioning, especially if you are looking for VC or financial advice.
PS. I am not YC reject, I never applied since I don't have a co-founder.