Subversion has a lovely little utility called "Blame" which will show you who modified a line of code and when, so you don't have to trawl through the history or the file looking to see when a line was changed. I've always thought that this was a feature that TFS could do with... until now.
It turns out that TFS already has this, but the guys at Microsoft have given it a rather more subtle label of "Annotate". Click on this and all of a sudden the file gets decorated with who checked in which bits and when! Then you can find out who to blame quite quickly! ;)
