If you have QuickTime Pro you can use QuickTime Player to export them with less bit rate to make them smaller.
If you don't have QuickTime Pro you can use another program that exports movies. Only QuickTime Player is locked without the Pro key. QuickTime itself is not locked so export is available in other programs without the key.
You could also use something like ffmpegX to create a lower bit rate divX, but that's not viewable without a divX codec which has to be installed separately.