QuickREx 2.0.0 [link]

QuickREx is an Eclipse plugin that creates a view in which you can enter in your regular expression and then try several different test strings to check if it’s the one you want. The expressions are checked “against the test-text on the fly, matches are highlighted and you can navigate between the matches. You can also navigate through groups within each match (if groups are defined in your regular expression).”

This is one Eclipse plugin that I don’t think I could live without. I use it constantly, whether build regex for part of an application, or even trying to search for some tricky bit of code in my system.