>I have a table of warrants with latitude and longitude, and I would like to be able to select all warrants within a given radius. I know I've seen this discussed before. Any of you math professors got a clue?

The simplest (combining database and maths) would be to select those which fall into a square of the same size - i.e. which differ north/south and east/west by no more than a given radius - that should reduce the number of hits with a single simple SQL call. Then among those, exclude any where N/S distance squared plus E/W distance squared is larger than your radius squared. The remaining guys are in your radius.