>heloo i just got a commodore 64 and was wondering if anyone knew a
>cost effective way to mess with them,

Well, the obvious thing is to take the SID chip out and put it in a
HardSID card which you can plug into your PC. But hundreds of people
have done that before and I presume you want to do something new!

The key things you'd be interested in, though, are the VIC-II chip for
video, and the SID chip for sound. Pin-outs and specs for those chips
can be found easily enough on C64 sites or in the C64 manuals.

Even without wielding a soldering iron, you can get some neat effects
by poking random values into the VIC-II's data registers, of course,
which again are easy to find on the net. Or take some SID tunes from
the HVSC, corrupt them slightly, and transfer them into a real C64 to
see what happens. (They'll probably crash but you might get some wild
noises first!)

You might also get some inspiration from some of the modding projects,
such as the MMC reader.

--Darren