Flip4Mac does a good job.....not paraticularly speedy in quicktime to WMV conversion - but creates good looking streaming and standalone Windows Media Player. Check out Compression Master www.popwire.com if you are compressing to various formats....very speedy...multiple format conversion...batches etc....not inexpensive but does a great job. Also Sorenson Squeeze - however it uses (and you must purchase separately) Flip4mac as a component to compress windows media...and I've found in head to head comparisons...Compression Master is faster.
One of nicest things about Flip4mac is ability to play Windows Media within quicktime player and inside your web browser (works great with Firefox) ...the quality of playback is lightyears better than with Microsoft's own Windows Media Player for mac....plus you can scrub through pause etc the WMV within quicktime...something that is hit or miss or impossible in MS WMV Player for mac Andy