I have owned three Canon cameras: a PowerShot A540, and PowerShot S1 IS, and a PowerShot SX110 IS (which I currently use). I've had mostly success with each one. The A540 was small enough to fit in your pocket, but still had a full manual mode, which is good for taking long exposure night shots. The camera did develop a small problem though; it would indicate a low battery even when the batteries were fully charged. I learned it's a common problem with these, and if you bend the contacts just right, you can pretty much fix it.
I really bought the S1 IS for the 10x zoom lens; I enjoyed using it to take pictures of airplanes as they flew overhead. This camera won't quite fit in your pocket, but it's not huge either. It also had a higher quality (and bigger) lens than the A540. I enjoyed using the manual mode on this camera as well. One area it was a bit weak in was autofocus, sometimes it was tough to make it work in low-light conditions.
The SX110 is the camera I use now, and I like it. The autofocus is much better than the S1 IS. It takes good quality photos, and I can fit it in my pocket. It still has the 10x zoom like the S1 IS, which gives you a lot of framing flexibility. Unfortunately, recently I've gotten some type of dirt underneath the lens, which gives black spots if I take a sky photo. I plan to take it apart at some point to try to clean this, but you really can't see it in most pictures.