yeah... minidisc is pretty portable. but you probably want to also be able to mix your music afterwards.... so, you should also get a decent sound card too.
or, if you want an all in one, guitar center is selling the roland 840? i think that's it.... for $500. it's very good deal. you get 8 channels i think of mixing and recording. you don't need any extra equipment, besides some monitors... or hell, your headphones.
or of course, there are the models Ari suggested.
these all-in-one type studios are very popular now. you should seriously consider one. though, you're gonna need a mic too. ....go to this web site and check out the mic section:
homerecording.com/bbs
very good site. most of the people there try to maximize their money.... so if you don't have much cash, listen to their recommendations. these are real musicians there.