Looking at my builds, I've built a new PC every year since 2003 except for 2007 when I went travelling. Well, it's 2010 and I've built a new machine for my kids. I've written about it here.
It's based around a Core i5-750 and an Asus P7H55D-M EVO. Made the move to a 64bit OS. I built the last kids computer in 2006 so this should last them until they want their own laptops. I'm happy to see gaming move over to a console.