I'm not that familiar with bards, but I don't think there are that many prestige classes that advance bardic music. The go-to bard prestige class is sublime chord (Complete Arcane). That gives better spellcasting, but doesn't advance bardic music.
There is a fun thing you can do with straight bard. Bardic knack (Player's Handbook II) is an alternate class feature that replaces bardic knowledge. It lets you use half your bard level (rounded up) in place of your skill ranks whenever you want. It doesn't give you the ability to make checks as though trained, but the feat jack of all trades (Complete Adventurer) does. As an 11th level bard, you would effectively have 6 ranks in every skill, including every craft, profession, and knowledge. This even includes knowledge (local) for every place that exists.
If that's not your thing, there's also lore song (Dungeonscape). That's also an alternate class feature that replaces bardic knowledge. It lets you add a +4 insight bonus to an attack, check, or save as an immediate action. It can be used a number of times per day equal to half your bard level (rounded up).