Lower the resolution and you can lower the size without lowering the quality, at least to some degree.
If the original format is 720 x 480 you can reduce the size to 320 x 240 and still maintain quality along with reducing the file size.
Good quality WMV is about 20mb per 5 minutes, you will still end up with a 480mb file.
FLV (Flash) is currently one of the best formats for the internet due to small file size and good quality.
You need to embed a player for this to work but it is a very good option. MOV is also an option, Quicktime has been a favorite for years.
It will all depend on what file size you are trying to achieve and what image resolution and quality is good enough.
