In my experience, pretty much every start up is hiring provided you're qualified and passionate enough. By their very nature, start ups can't possibly list things like expected salary or equity because those heavily dependent on what you yourself bring to the table. If you'd like a place to start when looking for start ups you'd be interested in, http://www.crunchbase.com/companies might be a good place to start.
In the words of Paul Bucheit (from his talk at Startup School 08), "I've never really had any problems figuring out what to do with more really great people... because they can usually just take care of themselves."
http://news.ycombinator.com/jobs (you already know this)
Apparently it's helped companies get funded, find startup employees, and help freelancers market their services... and has an easy user interface.
Has anybody else used GoBigNetwork?
If there is nothing listed email one of the founders directly and tell them why you want to work and what you can do (keep it short).
You probably won't get a job instantly, but 3 months down the line people will be contacting you before they post the open jobs.
If you would like to contact me you can do so at nathan (at) npost (dot) com.
To everyone else, I am the founder of CoNotes, which is another resource available for startup positions. Currently there are over 500 companies and 200 openings available. I'd love to hear people's thoughts.
Thanks.