Now that twitter has become mainstream (Even the Australian prime minister has a microblog) it can be useful to consolidate all of a contact's information into one place (instead having to monitor their blog, microblog, flickr account etc etc) which is where a service life FriendFeed (ff) comes in.
On ff you create create an account that sucks in all your other feeds (blog, twitter, identi.ca, flickr, digg, slidshare and so on) into a single place. All people have to do is to subscribe to that single account (probably via RSS or IM) and they get everything you are doing -- not just your twitters. At the time of writing ff supports:
That's all very well and good, but what if your network buddy does not have an account on FriendFeed? That's were ff Imaginary friends come it. You can create an proxy account and then add the external accounts your contact posts on. All the account types listed above can be added and anything not in the list can created using the Blog type which expects an RSS or Atom feed. If you are adding a Wordpress blog then make sure you follow this suggestion to get post titles to display correctly.
So currently I have 21 'real' contacts on ff, but another 17 proxy contacts setup, including @stephenfry. Not only do I get his twitter posts but also notification of his wonderful blog posts, all in one place.