Well, I think you're going to have to pay for most of these, but there's a list:
Weblogic seems to have some kind of connector development kit, but I don't know anything else about it.
The only free one I know of I wrote (most of);-) and it's not quite done: it's a jca-jdbc connector for the firebird rdbms. Its in cvs under client-java at firebird.sourceforge.net.
JDO implementations for use with application servers are supposed to be based on jca interfaces, however both the JDO spec and all the implementations I've come across seem to have serious misapprehensions about jca.