I'd recommend trying Netbeans with the Ruby Plugin or Ruby Mine. I've been using Ruby Mine some lately and am pretty impressed. Has a debugger that works well

I'd recommend trying Netbeans with the Ruby Plugin or Ruby Mine. I've been using Ruby Mine some lately and am pretty impressed. Has a debugger that works well, auto-completion, rake integration, click thru to declaration, etc. It's not going to be free ($79), but given JetBrains track record with IDEs I think it's a good investment. I tried NetBeans last year and it seems promising, but haven't used it in 6 months.