Hmm, looks like I was a bit too quick with my recommendation. Prompted by Marc's questions I conducted some more tests and currently it seems that mod_lisp2 is leaving some sockets open if the Lisp used is AllegroCL 7.0 - yesterday I only tested with CMUCL. This doesn't happen with AllegroCL 7.0 and Apache 1.3.
I'm also just building an Apache with the "worker" threading model and will play with this combo as well. More info to come soon, hopefully.
Nevertheless, if anybody is willing to give the current code a try - just do it and report here... :)
Cheers, Edi.