Some random thoughts:
- Bardic Knack(PHB II) is better than Bardic Knowledge(you can get your Knowledge back from Cloistered Cleric 1, or various PrC's)
- War Weaver might be a worthwhile PrC, pretty much all it does is getting more Buffs for less Spellslots.
- Somehow get more Spells known, than a Bard of your level. I'd use Feats/PrC to get a Spellbook and/or access to a Spellpool.
- Be a Draconic Creature with availible Feats, and/or dip Marshal to get a 24/7 Buffaura.
- Crusader and Paladin are awesome for a multiclassing Bard, provided you take some levelstacking Feats(IIRC found in Complete Adventurer, Champions of Valor and Tome of Battle).
- Consider Bard/Spellthief with Master Spellthief from Complete Scoundrel(usefulness depends on how you interpret the wording of the feat)
- For a Buffer, getting Persistant Spell is awesome, the Bard can do it with Spelldancer(Magic of Faerun) or Metamagic Song.
A Bard 4/Binder (1 + Improved Binding Feat)/Anima Mage 10 would make a truly versatile Charakter, Spells get better with the addition of Sublime Chord & War Weaver.
- Without early entry cheese(), it is not possible to fit Anima Mage 10 and War Weaver 5 on a Bard.
- Just replace Binder/Anima Mage with Incantatrix +any 1 level dip you like, if Pact Magic isn't your cup of tea.