Tome of Magic is yet another book I've yet to get, but I'm thinking about heading down soon to see a sale in a local RPG store, 3.5 book sale since 4E came out. Don't have ANY books besides PHB/DMG/MM and some Scarred Lands books, what would be best to get on a limited budget?
Spell Compendium, Magic Item Compendium, Unearthed Arcana, PHB II, DMG II, MM II & III, Eberron Campaign Setting, Magic of Eberron.
Other books to consider if you can't find the aforementioned or you have more spending money than you thought and actually bought all the aforementioned and still have some left over: Citsycape, Dungeonscape, Frostburn, Stormwrack, Sandstorm, Planar Handbook, Complete Warrior, Complete Adventurer, Complete Divine, Complete Arcane & Oriental Adventures (don't forget to email me if you buy this one, I'll reply back and send you the Dragon Magazine 3.5 update).
3rd Party Books: Any of the Relics & Rituals, Nyambe, pretty Much anything Green Ronin, Arcane Evolved, Transcendence, Gary Gygax's World Builder, Traps & Treachery I & II and Legends & Lairs: Sorcery & Steam. Alternately I highly reccomend purchasing The War of the Burning Sky print products through Lulu, you won't regret it.