Ian Johnston wrote a post on his blog detailing his bench power supply build:
My workshop has a couple of bench power supply’s, one is an old Farnell TOPS 3D 3-rail tracking job, and the other is a 3-rail CSI CSI3005XIII with Constant Current functions. The farnell is all analogue but has no constant current control, it has current limiting only. The CSI is good but doesn’t allow you to preset the constant current setting and thats what I want. So, rather than buy another PSU I thought i’d design and build my own, something thats directly suited for me and my projects.