AAAAAAAAAAAAAAAAAAAAGH (Sorry was the flash thing).
As far as i know, and i've been into web development for a while now, there's no replacement for Macromedia Flash MX for the linux O/s. It's good old dual boot mode for us i'm afraid. That or wine, and quite frankly wine does'nt agree with me. And we fell out last time i used it
Web development again is Macromedia's forte, closely followed by M$ with Frontpage (ugh dirty word).
Good old text editing will do you web development, but there's really no substitute for good ol dreamweaver.