canon 35mm f2 ef.

What camera do you use?
The Canon 35mm is around $300. The Nikon equivalent is around the same price.

If you use a cropped sensor camera (as opposed to full size sensor) you can have the Nikon 35mm DX f2 for about $200.

Silly remark that you probably already know, but if you use Nikon and can live with 50mm the Nikon 50mm 1.8 is around $150 NEW! You can get it used a bit cheaper but I would go for new.

@ melanie_o i got the canon t2i. i bought my 50mm 1.4 few days ago & i just love it. but the problem is, since i've a cropped sensor, 50mm works like 80mm. its too tight for indoors. so, i wanted to know about any cheap 30/35mm (like helios/used canon/even nikon) around $100-150

as i've invested all my money on 50mm 1.4, i want to get a really cheap 30/35mm lens

Sorry, I don't have much knowledge of Canon and their lenses. The Nikon have lenses built for cropped sensor and they are much cheaper and, in my opinion, absolutely superb. Won't work on your Canon though :-), sorry.

you can find m42 lens and m42 to eos adaptor at ebay