Try a program called Mcap, or Microcap. I think it's available[£free ]as a student limitied edition.

My first electonics thingie was a pulse unit for my tig, all done by trial and 'art of electronics' in microcap. It worked perfectly in the simulator but I think it needs added capacitors as it wasn't stable. I assembled it on one of them boards with loads'a'holes and was completly amazed when it worked. I still haven't actually built it.