Recently I was given a Pentax K1000 film camera and it got me thinking about using the 50mm F2 on my canon 550D. I have the adaptor on the way from Ebay.
But I have found that as well as K mount lenses I can use old M42 lenses as well(I now have a Zenit camera on its way with the helios lens:-)

Can anyone recomend good K mount or M42 lenses?