A sidebar is a bar that drops in when everything is in place and cannot be set one pin at a time. Oldest use I know of is the abloy lock, then the briggs and stratton general motors auto locks, then of course, Medeco and other HS locks, assa, primus, etc. Oh, and for the medeco, our own Jon King has figured out how to set the pins one at a time.
Quick list from the highlight locks I've opened. Question marks mean that the lock was normal but unknown model. Also, I try to ignore imbalances in practice times (for example, I rank Medeco where I think they'd fall for folks without a solid year of practicing them):
With every one of these, the way to really improve is to follow db's build-up method. Start with a couple of pins and add in more while scrambling them up.