This is an update to a previous post of mine which uses the RAND() method. Using the following code, you can retrieve a random row much, much faster (MySQL 4.1.x/5.0.x), with thanks to Jan Kneschke:
SELECT <COLUMN> FROM <TABLE> AS r1
JOIN (SELECT ROUND(
RAND( ) * (
SELECT MAX( id ) FROM <TABLE>)
) AS […]