I think the previous posters have you covered on software suggestions. I just use the Macromedia flash video tool to export my existing AVI files to flash video format. It sounds to me like you may be expecting too much from your video compression codec though. Compressing video is nothing like compressing audio in terms of file sizes. You aren't going to be able to compress any 30-second video down to 600k and have something that is pleasant to look at, and this is especially true with older .swf video files which use much lower quality compression. For medium to high bandwidth users, I compress my video at 200k/sec with audio compressed to 32kb MP3 format. For Flash 8 video, this seems to give me the best compromise of quality versus bandwidth for a resolution of 320x240, which seems to be the defacto standard size for streaming web clips. So for example I have a 136 second clip that clocks in at 4.4MB, at that bitrate, but my video has very little motion, so it's more compressible than most video. For a 30 second clip, you might be able to get yours down to around 1MB if it's low motion or lower resolution. You can see the results at these bitrates on
The Real Estate School homepage. There's a Flash video player built in to the picture on the left side of the page. The first video is 4.5MB and lasts about 137 sec. If you go with more compression to get smaller file sizes, the quality starts to drop off pretty quickly once you get under 200kb/sec. Flash 7 video format is even worse...if you look at that same page with the Flash 7 plugin you'll get the 300kb/sec Flash 7 version of the same intro video which clocks in at 5.6MB. Despite being a higher bandwidth video and having a larger file size, the video quality is slightly worse than the smaller Flash 8 version. You'll notice that neither of them are as small as an MP3 file of the same length would be. That's just not possible with video.
Hope that helps give you a better idea of what you can expect in your own videos. I believe some of the new 3rd party flash video tools can give slightly better results than the Macromedia Flash Video exporter, so if you go that route you might be able to get slightly better results, but if you're using .swf format you shouldn't expect results that are comparable to using the more modern .flv format.