Compressing images to reduce hosting space useage

Hi,
I take a lot of photos and I upload them at 600x400px onto my website.
At this size, however, they are still up to 300kb files and 60 or 70 of these in one go eats up space.
I use Digital Photo Professional and by reducing the image quality can get the files down to about 80kb, but they are pretty poor quality.
Does anyone know of any software available that can help me resize my photos to smaller file sizes without losing so much image quality.
Not strictly a specific WP issue, but I do use WP for my sites so I’ll give it a go.