Plenty of expansions available!
Shadows of Undrentide and Hordes of the Underdark are both 'official' expansions are are well worth the money (HotU is wonderful, I thought).
Bioware also has other expansions available for download (
Bioware store linky )for a modest price (around $8 I thhink). I played one of those (Kingmaker) and while it was well done, it was short, not challenging, and had little replay value.
Community created modules (
Nw Vault linky) range from really good to pointless. The Shadowlords/Dreamcatcher series and Midsummer Knights dream Series were pretty good. The Shadowlords/Dreamcatcher series is around 6 modules long, and if you start off with a new character you can level up to around level 18 by the time you are done (IIRC). Nice and long with an entertaining storyline. The Midsummer Knights Dream series is only 3 linked modules, and they have a good storyline as well... tho not nearly as long as the dreamcatcher series. But be aware that many community expansions require you to have both SoU and HotU installed (for graphics and gameplay modifications).