a few options...
If you're using Outlook, then you can just right click on the image in explorer, send to, mail reciepient and you will be prompted if you want to compress the images and they'll be attached to an email for you. (never used this facility myself so don't know how well it compresses the images or what size t compressed them to)
IrfanVIEW is great for batch processing, I use it all the time and has loads of options.