I have added a Common Lisp-like condition system to the Parenscript Object System (PSOS). Parenscript now has HANDLER-BIND, HANDLER-CASE, RESTART-CASE, RESTART-BIND, INVOKE-RESTART, and SIGNAL.
The patch that adds this is here: http://github.com/gonzojive/paren-psos/commit/6578ad223515dc2c1ddf49346f4baf... and totals about 200 lines, plus 200 lines of test cases. It could probably work without a type system at all, but it will require some runtime code no matter what.
The whole PSOS system is backed by a test suite that uses CL-Spidermonkey. Take a look at PSOS here: http://github.com/gonzojive/paren-psos for more details.
Enjoy!
Red