Dragonlance. If you were playing D&D in the 80s, you likely read the Dragonlance fiction and/or played the adventures. While I didn't much enjoy the Dragonlance modules (can you say "railroad"?) I thoroughly enjoyed the fiction, maybe too much, and enjoyed the Dragonlance Adventures Hardcover supplement for AD&D.
Dragonlance Adventures (1e) gives you knew and revised classes and races for your AD&D campaign and is on sale for 2.99. Also clocking in at 2.99 is the Atlas of the Dragonlance World (1e). For less than six bucks that's a full on AD&D campaign.
Ot, if you want a AD&D 2e supplement, snag PG1 Player's Guide to the Dragonlance Campaign (2e) for 2.99
Want to play though the original 14 adventures of the Dragonlance series?Dragonlance Classics: 15th Anniversary Edition (2e/SAGA) is 5.99.
Can't get enough Dragonlance? This link will take you to more Dragonlance than you can shake a stick at :)