I noticed a while back that Dirk mentioned Roger had now won titles on every surface for three years in a row, and wondered who else had done it. The answer is, just one. Here's the list of players who have won on every surface in the same calendar year:
Connors (72, 74, 78)
McEnroe (79, 84)
But this is rather contentious, since my definition of "all four surfaces" is grass, clay, outdoor hard/carpet and indoor hard/carpet, due to the difference in playing conditions. If hard and carpet were considered to be entirely separate surfaces, then Sampras also won on every surface in 1998, in Philadelphia (indoor hard), Atlanta (clay), Wimbledon (grass) and Vienna (indoor carpet).
For more on this, see my insanely detailed thread here: The Great Big Super-Duper Title Resource Thread
I list all the players who have won titles on every surface in the course of their career, including a particular journeyman who inhabits my avatar.