I am trying to find the right ones for myself, but options seem endless!
I'm a big fan of Scope at the moment, which aggregates a number of services (single handle for each service, though).
What sort of `manage` do you mean?
I used to use Seesmic (which has been acquired by HootSuite it seems), that seems to be the defacto standard for a marketing sort of approach, at least from what I hear.