The ratios used are 16:9 and 16:10, with 16:9 used mostly on TV's and 16:10 on LCD monitors. It's easy to calculate more resolutions.
Here are the some examples:
1920x1200 - 16:10 ratio
1680x1050 - 16:10 ratio
1280x800 - 16:10 ratio
1280x720 - 16:9 ratio