How much is cheap then? If your only talking around the �20 mark then (assuming your recording onto your PC) I would be most inclined to go for a dedicatede computer mic from a good audio maker like Labtec.....If it's not for the PC then a cheaper Sennheiser, Audio Technica or Beyer Dynamic microphone which should all be around �30 to �40 should fit the bill nicely.
Agree with what has been said (Behringer also do a range of good, cheap dymanic and condenser mics) but I would also avoid the mic in of PC sound cards. Most PC sound cards have a terrible mic pre-amp which can be avoided by using an external mic pre-amp or a mixer before plugging into the PC line in. The beauty of a mixer is that it will give EQing options and often effect loops so you can process the signal before you record it (post recording processing will require more expensive audio capturing software such as Soundforge etc).
Thanks for agreeing with me Buttons but I have to disagree with one thing you said....I would never EQ anything from any source before recording as you are then left with that permanently on the track....Plenty of home recording studio software including Fruity Loops, Cubase, Soundforge and Cakewalk are all freely available on WinMX and Kazaa so with a little practice any results can be achived.