Everybody forgets about SICL. It's one of the few new CL implementations that's not proprietary or copyleft.<p><a href="https://github.com/robert-strandh/SICL">https://github.com/robert-strandh/SICL</a>
I've worked on PAIP, and I think the GitHub.com version - <a href="https://github.com/norvig/paip-lisp/">https://github.com/norvig/paip-lisp/</a> - gets more attention than the GitHub.io version linked here. The GitHub.io version automatically gets updates, I think, but I'm not verifying the Markdown works over there.
I really like this, as from an outsider it seems that CL doesn't have a community and the few packages it has are more like building blocks for customizing and implementing you required functionality rather than packaged black boxes. With all those new languages, it appears that the value proposition of CL is dwindling, static checking feels primitive, macros are easily attainable now, and live runtime image manipulation misses the point on the world of short lived containers.