I did 15 days in Europe last spring (mix of business and pleasure, among UK, France, and Germany) with just the Red Oxx Air Boss. It was a trial-by-fire of the suggestions from http://onebag.com and I'm now definitely a convert. Make sure you have travel socks and briefs (so they'll dry overnight after washing).

The Red Oxx was my companion for most of my 150K+ miles last year, and has been worth every penny. (Plus it fits in every overhead in the AA fleet, and never having to gate-check is lovely.)