The most important thing is to make the file size as small as possible. If the recipient wishes to view them on screen rather than print them you should reduce the resolution to 96dpi which is the same as a typical monitor.
Depending on your camera settings most pictures will probably come out at about 300dpi so reducing the resolution will make a big difference to the file size and, therefore, download times. If your software will do it you can then reduce the size at which the picture will display - 800 pixels equates to approx 8.3 in at 96 dpi.
If the software that came with your camera there are a couple of freeware programs that may be worth looking at Irfanview and Photofiltre both of which you can download from
It sounds complicated but is actually pretty straightforward and you should be able to get to grips with the basics in about half an hour.
PS If the recipient wants print quality images and is working with dial-up it might be worth considering putting the pics on CD or DVD and mailing them. Windows XP includes the facility to 'burn' CDs in Media Player so, if you don't want anything too sophisticated, you don't need to invest in new software.