The 2 most common progams would be PaintShop Pro (PSP) or PhotoShop (PS). Either one will do what you need. I would suggest trying before you buy. You can save the images in any typical web format; GIF, JPG, PNG, etc. The idea is to make the images as small as possible in terms of file size. Always keep in consideration the amount of time it takes for a page to load. Not everone has a broadband connection.
