As for the speed there are at least two issues. First off, free users can only download one file at a time. I can't do anything about that.
Second, the speed you are getting is not due to rapidshare itself. My downloads are very fast and I frequently hit my limit (premium account). If other sites are fast for you then there is something going on between you and rapidshare. There have been issues recently such as DNS poisoning that may be slowing down portions of the internet. This would impact more than rapidshare and would be beyond their ability to control.
I sometimes load things to megaupload so maybe that will work better for you. The other sites simply do not retain the files long enough or work well enough to justify my time uploading to them.
You might want consider mirroring these files on another server. Others will likely appreciate it and (hopefully) do the same for you when you run into rapidshare links in the future.
Enjoy the tunes!