Combining .rmvb (video) with .srt (subs)

Hey /tech/,

Since VobSub doesn't support .rm or .rmvb, is there an alternative sub muxer for said video types? Or should I just convert to .avi first, in which case, what's the best freeware video converter out there?

And yeah, I rather not go through the hassle of making a hardsub.