Word Reference--This is a fantastic website for looking up meanings of words (Spanish to English, English to Spanish).
BBC Languages: Spanish--A comprehensive and lively collection of free audio and video courses for both beginners and intermediate learners.
Coffeebreak Spanish--Excellent Spanish Podcast aimed primarily at beginning and early intermediate learners.
Spanish Language and Culture--Maintained by a Spanish professor at Colby College, this website contains grammar exercises and some excellent activities which use songs, videos and even poems to help improve your Spanish.
Study Spanish.com-- Features a wealth of tutorials for grammar, pronunciation, vocabulary and verbs available for free and mostly for beginners and intermediate learners.