Idea #1) Kickstarter in a box
It seems like every day I see a new story or blog post about X new product that was funded on Kickstarter. But what do the projects that get funded have in common? Usually they tend to have high quality videos, great photos of their prototypes, good rewards, clear and effective copy, etc.
However, the people with neat projects may not know much about video production, they aren't photographers, they may not have a website for their product, they may not be great writers, may not know marketing, etc. So the idea is to have a consulting firm that would offer a full service Kickstarter package. You'd get the creator with a great product a website, a high quality video, good donor incentives, great copy, high quality photographs, help marketing etc. In exchange you could take a % of their funding if successful, just like Kickstarter does.
Idea #2) A YC/Techstars consulting firm
The basic idea is that they'd obviously be a prior team or group of individuals that participated in YC/TS who would help hopeful applicants refine their applications, prepare pitches, interview practice, investment advice, etc.
Idea #3) Freelancer deals
The basic gist is that the site would sell the services of freelance designers, developers, writers, marketers, etc, Groupon style. Say you're a good designer but you're looking for work. You normally charge $60/hr. You could offer a special to this site to do 2 hours of work for X people for $20 instead. This would probably be enough time to make a decent logo/layout for someone. Although the designer may be doing work for far below their normal rate, their portfolio would be featured to everyone visiting the site. In addition they'd have the chance of recurring work at their normal rate from anyone who bought their deal. This also gives the buyer a chance to try someone temporarily at a minimal expense before making a bigger commitment.
Idea #4) Teach me
One on one live video music/gaming/etc lessons. Education related startups seem to be a really hot market right now so maybe some of these already exist. The basic idea is that you'd pick a niche and have a site of professionals in that niche. Say musicians for example. You'd be able to pick a guitar player that you like the style of and the site would allow you to take live streaming video lessons for $X/hr. The instructor would be able to give you immediate and instant feedback, etc. You could do this for a lot of industries I'd imagine.
Idea #5) Codecademy for investing
Many people are somewhat clueless about investing and saving for retirement. This site could help teach you on a basic khan academy level about the fundamentals of investing, guide you on the right types of investments for you based on info you provide, help you sort the different packages by various investment firms, etc.