Well, that is going to depend on the meaning of the word "cheap".
If you've got a dSLR, two of the major brands (and the #3 brand has them used) have a very inexpensive 50/1.8 lens. That's a great place to start. I did, until it reached it's demise on the streets of NYC, shortly after visiting B&H's ...megastore. (You know the overhead track at StarTours, they use the same system)
With a P&S, you'd either need to bump up the ISO or make sure it has a fast lens (which is probably at the most wide-angle setting). A monopod or tripod can help, but only a little compared to large apertures or high ISO.