Historical version 5 of Metro Newspaper (view current version)
A free and reasonably good quality newspaper available from Tube and bus stations. It's popular, so does tend to run out quite early, generally by the end of rush hour. You may well find some copies left in your Tube carriage, though, at least until about lunchtime.
It occasionally has offers of free coffee/sandwiches/etc from various London sandwich shops; Benjy's is one that I remember.
It's produced by the same company as the Daily Mail and Evening Standard, so some people complain about it being too right-wing. It also basically rehashes all their stories and plugs the other two. Although that said the 60 second interview is always worth reading.
There are editions for other cities, too — Manchester definitely and possibly Edinburgh too.
(I'm sure I already wrote this page, but it might have got eaten in the server crash --Kake)