For the domain that I am currently looking at, the .com and .net both just redirect to some generic keyword search page.
There are always good names available. You don't need to stick get on the front, or use a .net name, or pull a del.icio.us. Just fire up instantdomainsearch and find another name.
And, I have been surprised to find that if I keep banging away at it, I do eventually find a good name. I was looking for a name for a new site to host some Flash brain games I've been working on, and it only took about 20 minutes of searching to find a domain I loved. I had to make up a word, but there aint no harm in that, I reckon, as long as it isn't too long or too hard to spell.
It might be easier to make up a new name than to settle for .org. A site like boingboing.net does well enough - though I often forget the URL because the .net isn't part of the brand. I've seen links to boingboing.org/com, which might have an effect on search rankings. If you do choose .org, make the .org memorable.
That didn't work for my most recent domain. Try http://www.bustaname.com/ or code your own for increased speed/flexibility.