How to Get a Great Mix

TweakHeadz Lab: Recording Guide - Thorough resource for all music recording topics

Recording Magazine Mixing Articles - Music Mixing tips on EQ, Compression good instrument tones
 
Crunkbox 20 Tips on Mixing - Lots of good, common sense mixing advice

Audio Mixing Tutorial by Dan Kury - Great mixing advice including tips on MIDI instruments

Complementary EQ - Christian Cummings on using the full frequency spectrum - with EQ and in your arrangements.

Digital Domain: Mixing Tips, Tricks - Mixing advice from a world class Mastering Engineer

Harmony Central: Recording Forum - A great community resource - search for practically anything and you'll find an answer (or opinion..)  Check out Recording Tip of the Day

TAXI's Music Biz FAQs contain songwriting tips music-business information, and articles on Film & TV Music placement.