It is always going to be a compromise, size vs quality. Until the next generation compression comes out.
photogguy, the first question is really: Are you OK with YouTube / Vimeo?
If so, I suggest using the H.264 Apple TV preset. Going to be a larger file size, but less than the native codec you're editing in so your upload time won't be a zillion years.
You can make your YouTube channel look really nice. And unless you're trying to sell yourself as a web guy, you don't need to code an entire player yourself into your own page.
If you want to skip the 3rd party hosting & use your own website, then .flv is going to be the best way to go. I'm not that big a fan of flash, but it is the most likely to work on the most computers. You also have to embed your .flv into a .swf, which is more code that can be tricky or can be easy.
FCP / Compressor can't export to flash w/o buying more software, so this isn't a free way to go.
Finding the best .flv settings really depend on what you consider "best." I've had clients that need things under 10MB, where others need the video to be exactly 320px wide.
Anything multi-pass is going to take longer to export, but will be much higher quality.
If you're doing a lot of exporting, it is probably a good idea to look into Matrox Max. Hardware h264 acceleration that works perfectly in FCS & has better presets than what is in Compressor out of the box.