I built a custom one for ARES/RACES in my county. I used Access. I don't know of any available commercial or share/freeware app that is available for ARES/RACES use.
There is at least one simple DOS based logger for Skywarn operation- called Skywarn-EOC. Check http://www.n9mxq.net/skywarn/
for more info on that. I believe it keeps track of member stations, contact info, etc. but I would not call it a membership database.
If you're not afraid of Access and have a copy of it, I think you'd be better off with that, honestly. The nice thing about the little DOS logger program is that you can export your data out of Access into the data files of the logging program- so you can import your membership database into the software then use the DOS program during a Skywarn/ARES activation to track who is where and the situation.
Just some thoughts... good luck.
Marlo Montanaro- KA2IRQ
Monmouth County ARES DEC
Monmouth County RACES Radio Officer