One is general entertainment (think 16 - 24 demographic, male, using 4chan and facebook). Although it's got a USP, during the time spent coding the competition has increased (which I view as a positive). I do have an edge but it will take time to build user base and to drive advertising money.
Other one is SaaS aimed at power-users of one particular global social media channel. Senior marketing specialists, PRs and similar type of folk. Very innovative tool, narrow niche, big subscription price. This one has a better short-term cash generating prospect compared to my first startup.
Browse through websites and try to identify issues with design/marketing/or whatever you do, then get in touch with the owners and try to help them solve the issues. You'll know instantly (judging by the response) whether there is potential for you to work together. Nothing endears you to the potential clients more than free advice.
This method has got a low success rate, so you'll need to go through a number of websites before you hit a positive response. And it's important to make sure you've got a "presence" (like ekpyrotic and tagabek said)
It may make things easier if you target websites that are based in your area (or within a driving distance).