I've discovered that schlepping the Canon XSi around the time is a hassle, it's just too big. On a recent two week trip to the UK and Ireland I found I was leaving it in the car on most tours.
I've since purchased a much smaller Parasonic Lumix FZ 35. Touts an Leica lens. Not a DSLR technically as the viewfinder doesn't look directly thru the lens but at the screen. Seems to work very well. Can shoot RAW if you're interested in that format. Ain't pocket size but more convenient than the big Canon.
Love the Lumix line. My first one was a wallet sized FX9 and I've given that to my DD and replaced it with a TZ1 (they're now up to a TZ5 or 6?). Small, lightweight, big LCD screens. They're great "daily drivers." I only break out the 50D for sports or other serious low light work.