Just a summary, please add other profilers here (please edit document, do not comment) or a rating if you know how good these are:
http://www.appdynamics.com/products-free-download.php - completely free
http://www.appdynamics.com/30-day-trial.php - 30 day trial available; $? for a license
http://smartbear.com/products/development-tools/performance-profiling/ - 30 day trial available; $599 for a node locked license
http://www.dynatrace.com/en/development-team-edition.aspx - no trial; $? for a license
VisualVM - comes with the JDK in version 1.6 (so it is free)
If you want to use App Dynamics Lite in Openfire, you may want to add these parameters to the JVM:
#All these setting relate to a CentOS installation
#This is the installation path to the javaagent.jar
#AppDynamics brings a Flash/Flex front end that needs a special port. 9091 is not the best choice, but possible and in our case dicatated by a firewall
#That's the IP of the server. We installed agent and viewer on the same machine.
#Appdynamics requires a folder to write to. In this installation, the profile logs are written in the folger were the OF logs reside.