yclist has a few errors, so not sure if it's all 100% accurate.
To name a few:
xobni - bought by yahoo and now shut down (listed as active)
like.fm - dead, but listed as active
Exec - listed as active, but was bought by Handybook
Bump - listed active, but dead
According to it, 46 companies are "dead", 52 are "exited" and 445 are "active".