Downloader Pro from
http://www.breezesys.com/ is quite possibly the program you saw. Its file renaming system is amongst the best around, ahead of anything in Adobe or iView. You can search and replace, slice and dice (ie chars 5-9), as well as more conventional things like adding a prefixx, suffix or sequential number. I'd recommend you get the bundle with Breezebrowser Pro. The can also write IPTC metadata into Canon and Nikon raw files - whether you want to do this is up to you!
Another program to try out is PhotoMechanic from
www.camerabits.com. Like the Breeze products, it's much faster than Bridge.
John