If it has to be Flash, then Sorrenson Squeeze seems to be best option.
There are two versions of the software package. One version is just for Flash, and a more
expensive version(Compression Suite) will do Flash, Windows Media and many of the same formats that Compressor will do.
Frankly, when compressing for broadband, I’ve gotten better quality with QuickTime/H.264. I’ve gotten a lot af great feedback from clients about the quality of the QuickTime video. As a result, I use QuickTime/H.264 whenever possible, and I use Flash only when compatibilty is an issue.
One note, however, the QuickTime H.264 requires QuickTime version 7.
G5 2.5ghz DP, 2.5Gbyte RAM, FCP 5.1.2, OSX.4.8
QT7.01, Kona2 (v3.2) w/Kbox, Atto UL3D, Medea RTRX640, Huge MV 1.8Tbyte, Radeon 9800XT