I use a batch resizing program for family photos and stuff I post online.
http://www.jklnsoft.com/
I am sure there are cheaper options that do mostly the same thing, but at the time I wanted something that worked without trying out a dozen options. It is pretty simple to use.
However, if you are running windows XP you should be able to use the
Image Resizer Power Toy, I am not running XP right now so I cannot confirm for sure but I am 90% sure it does batch jobs.