Postfix (and I believe other MTAs) allow "address extensions".  These are 
parts of the local part of the address which are not interpreted by the 
mail system.  Thus, with Postfix, an address in the form of 
local+ext@domain will be handled as local@domain.  (Actually, it's a bit 
trickier than that, but by default that's what happens.)

The suggestion I've seen (and which I now use) is to use the extension for 
tracking the source of email.  Thus, I am registered with Bugzilla with 
+bugz as part of the address.  I can easily use this both for automatically 
sorting mail into folders and for seeing who is handing out my address to 
the spam generators.

The one limitation is that I don't see a convenient way to add an extension 
if I am sending mail from evolution.  In particular, I'd like to be able to 
use extensions with mailing lists even when the mailing list checks for a 
registered email address before forwarding a message to the list.

While I could probably add (many) accounts which never attempt to receive 
mail, this seems cumbersome.