@mrenglish - If you're going to get your ccw, if you have a shop with a range and rental guns, it will be worth it to go try some different guns to get a feel for all of the options out there. If you don't have that option, and you are comfortable with a semi-auto, then I would suggest looking into the Ruger SR9c or SR40c or the Smith and Wesson M&P Shield in either 9 or 40. You have higher capacities with the Rugers, but the Shields are single stack magazines and a bit slimmer overall. Another option, if you want something a little more hard hitting, try out the Springfield XDS. It is one of the slimmest, best made compact 45s on the market today, but will set you back around $600. Now, if you aren't as familiar with semi-autos, and want good, no muss no fuss reliability, check out any number of the Charter Arms revolvers, or any of the Smith and Wesson J-frame revolvers in 38 or 357. You can't go wrong with either company.
@baron - The SR series don't come in 45, and as far as I know, there are no plans for them to make one. It is such a light, compact gun, shooting 45 through it wouldn't be comfortable IMHO. If you're wanting a good compact polymer 45, then the Springfield XDS is the way to go. It's brand new, but a lot of them have hit the market recently. I work in sales for a gun distributor and Springfield really did it right.