Hi Rob and welcome to the Q&A Board!
I rarely take inside photos so I use the little flash that I got for my Nikon (SB30) which works like a slave flash. I've heard a lot of good about the Vivitar DF200 made especially for digital cameas. It supposedly "learns" whatever digital camera you're using. I know some S2 users who seem to like it. I haven't tried it so I can't say from personal experience.
Here's some information about slave flashes:
http://www.digicamhelp.com/digital-camera-slave-flash/index.htmSometimes I really miss my FZ3, but I concur about the flash. It's a great entry level 12X zoom camera which takes excellent photos in proper light. I just found that it didn't have the level of sophitication I'm looking for after being into photography for more than 30 years.