How do I reduce the size of a 100MB .flv file so it will stream better from my web site?

That depends greatly on what format the original clip is, and what software you
have access to. Hopefully you have AfterEffects CS3. You can render the
original clip from AfterEffects as an flv, and decrease the physical dimensions
of the clip, the frame rate, and the bitrate. Just from personal experiences,
I'd say you could cut the 100M down to probably about 60M.......maybe a little
more. If you have AfterEffects, just play with the settings and see what you
can come up with. If you don't have AfterEffects or Premier then there really
is nothing you can do that I know of.

Thanks for your , but the file I have is already in .flv format. I don't have the source video. Is there some way to use Flash to make the file easy to stream over the Internet?

I still think you can import a .flv file into After Effects.