I'm giving away free ad space for early startups
selfdebugging.com
selfdebugging.com
http://www.techcrunch.com/2007/09/18/techcrunch40-session-6-...
If you're starting a new site, graphic ads can be very jarring to new users, especially if they're just trying to figure out what your site is all about. On the other hand, textual ads can be very subtle, but still useful to any startup - if anything, just to help them out in terms of Page Rank.
AdBrite's http://www.spottt.com/ might be a good option (soon).