I invite you to try out BoneCP -- it's free, open source, and faster than the available alternatives (see benchmark section).
Disclaimer: I'm the author so you could say I'm biased :-)
UPDATE: As of March 2010, still around 35% faster than the new rewritten Apache DBCP ("tomcat jdbc") pool. See dynamic benchmark link in benchmark section.
Update #2: (Dec '13) After 4 years at the top, there's now a much faster competitor : https://github.com/brettwooldridge/HikariCP
Update #3: (Sep '14) Please consider BoneCP to be deprecated at this point, recommend switching to HikariCP.
Update #4: (April '15) -- I no longer own the domain jolbox.com