Fotosizer is a freeware batch image resizer tool that lets you resize your pictures to the desired resolution in just three steps. Just add the folder or the photos to resize, select the desired resolution and click start.
This is one program that is going to find a permanent spot in my computer. It will help my mom resize her photos before uploading them to blogger, saving her a lot of space (blogger provides only 1gb of storage).
Fotosizer is for Windows only, there are no Mac or Linux versions.