Wade, arguably you could say that either of the three main web formats - Windows Media Player, Quicktime and RealVideo could be used on either Windows or Macs.

But realistically, wmv files are best only for Windows users and Mac users seem to prefer Quicktime files.

Checkout sites that use lots of web video - CNN, www.maxboxing.com, etc. and see what they're doing.

PS - I'm Stateside also.