You can also "upgrade" your Citibank card to an Citi/Aadvantage World MC -- to accumulate AAdvantage miles if you fly AA/Oneworld partners.
Citi also launched a membership rewards type program that lets you accum. points toward shopping, travel, etc....so you could link your existing Citi card to this...
I recently became a Chase/Continental MC holder -- and in 3 months have added about 16,000 one pass miles between utilization and sign-up bonus miles.