Photo Resizer is a freeware for resizing photos in a quick and easy batch mode. It offers all popular resizing algorithms and converts all format images to JPEG file format. Photo Resizer is the perfect tool for those who store their digital pictures and images on their PC and who want to resize, compress, convert, create copies, create thumbnails, import or organize photos. This version is the first release on CNET Download.com.
It's small (1.5 mb), easy to install, concentrates on one function (batch compressing) and does it well, very well designed interface, pretty intuitive to use, processes images very quickly, outputted images can be 10% of the original and look great.
It doesn't pick up the difference between portrait and landscape images, fairly big problem if you have a mixed batch of photos.
To be quick, my mom asked me to upload photos of her recent holiday to Flickr. 165 photos were 390mb, Flickr only allows 100mb upload. I found this great program, and got the photos down to 36mb (10% of the original batch!) and it took about 10 minutes.
She had no portrait photos, so this program was the ultimate tool for the job. The only con is resizing a batch of portrait and landscape photos, the output photos have white empty space either horizontally or vertically. So, you have to turn the originals landscape, resize, and then turn the optimised ones back to portrait :)