I'd like to recommend the Feisol CM-1471 carbon fiber monopod.
Over the years I've had Bogen and Giottos monopods that ended up turning into constant struggles with locks.
I lost the Giottos recently and picked up the Feisol.
It seems well-made with beefy tubes and smooth locks. It extends high and collapses to a small length; comes with case.
I bought my Feisol CM-1471 Rapid in May 2010. It's still going strong. OTOH, so are my Manfrotto heavy-duty, one-hand action Neo-Tec (2006) and light-weight Manfrotto 676B Digi (2008).