Well there are a lot of ways to go on this. For simple sound effects I think a lot of people use sfxr. For music you can use any kind of sampling / sequencing program. I’ve recenlty discovered pxTone and like it a lot for it’s simplicity. Audacity is also a great app for sound recording either for voices or for samples for another program.

Propellerhead Reason is really awesome and I’m using that but if you’re looking for something to use this week-end that probably won’t do.

Another vote for ModPlug tracker – I tried it last time I did Ludum Dare, and found it quite easy to use.

I use either LMMS or Musagi. I know nothing about making music and I can sometimes get decent results from them despite that.

I’ve used LMMS and it’s pretty cool. If you use it I’d recommend playing around and learning the interface, since it could be a little confusing at first.

PXTone is the way to go for simple chiptuning without using a tracker (I told billknye about it). I would also recommend Renoise, but it’s not free (however you can get a demo).

cheap keyboard (or in my case decent keyboard, just 1000 years old) with some editing functions, though I think I am going to skip music this time and use that time to polish the game

I’ll be cranking out something with FL Studio XXL, but that’s because I’m incredibly familiar with it. My last game was SILENT.