Irfanview is a free one, so are Windows Live Photo Gallery and Picasa. Then there's the Roxio suite and Photoshop if you want to pay.
This is a real noob question, but here goes: I have a number of pictures that I want to post to a service organization's website. All the pictures have a width of 1080 pixels. The website will not accept a width greater than 470 pixels. How can I reduce the size of the pictures to the required width? Do I try to crop them, or can I somehow reduce their overall size?