My recommendations for some autos under $600.
Semi-Auto
Smith and Wesson-
3rd Generation-
5906 9mm:
4" barrel, 15 round capacity, ~$400-$450. One of the finest 9mm's ever made. Though they don't make the 3rd Generations anymore, so you'll have to find them in listings like Gunbroker.
6906 9mm:
3.5" barrel, 12 round capacity, ~$300-$400. Fantastic for CCW. Same story on availability.
(Other models to consider: 908, 910, 915)
M&P Series-
Any of the M&P's would do you extremely well. They generally have a bit slimmer profile than the Glocks, without compromising any reliability. They have good capacity, and won't ever let you down. Full sized-compact and different calibers. ~$450-500
Ruger-
SR9-
Great gun by Ruger. Slim Grip, Good Accuracy, Reliability and capacity. Full size-compact. ~$400-$450.
Revolver-
Ruger:
SP101-
.357 magnum versatility. Comes in various lengths and variations, but 3" barrel is a very nice length. "Just the right size". 5 shot capacity. ~$500
GP100-
.357 magnum versatility. Larger and heavier though, and you'll have to feel the grips to see if it fits your hands. Good for absolutely anything, but will be very hard to conceal comfortably. ~$500
LCR-
.38 special. 5 shot capacity. Small grips, low weight, reliable, hammer-less, snub nose, and easy to conceal. ~$450
Smith and Wesson:
Snub Nose Options: (637, 642, 638, 60, etc...)-
J-frames are fantastic weapons that just about everyone loves. 5-shot capacity and lots of options ~$400-$500.
K-Frames (Models 10-19, and more)-
.38-.357, these are perfect "all-around" revolvers for carry, range, home, and vehicle. You can find them in all kinds of conditions for all kinds of different prices. Probably ~$350-$550.
I hope this helps you and gets you off and running.
~LT