My carry gun is a Makarov. The main thing it has going for it is that it's just so darn reliable. Mine has never jamed. I have not tried this, but I bet I could throw it in a mud puddle, then dump sand on it, and it would probably still work.
It's also cheap, as has been pointed out.
It is easy to hide because it is thin. Much thinner than a Glock for example.
"How much do they weigh?"
I don't know exactly, but they are all steel. They do weigh more than most other pistols of similar size. However, it is not too heavy for carry. After a while, I almost forget I've got my Mak with me...
"Do they make a good CCW?"
Yes. On a scale of 1 to 10, I'd give the Mak an 8 1/2, maybe a 9. The only real dis-advantage to the Mak is the caliber, it would be cool if it were 9mm Luger. But as other members have noted, the 9mm Luger round is too powerful for the Makarovs action. The 9mm Makarov round was designed to be the most powerful round that could be used in a small blowback pistol. I don't feel undergunned with the Mak, but it would be nice if it had a little more punch...
"Where do you find a decent holster for it?"
I made my own holster out of a old IWB one I found at a gunshow for real cheap. After a few atlerations, it made a great Mak holster.
"Someone mentioned .380 versions"
Yes, you can find Makarovs in .380 ACP or in 9mm Makarov (aka 9X18 ). There are also some .32 NAA conversion barrels being made, they sell them at Makarov.com
9mm Makarov is superior to .380 ACP. It shoots a slightly heavyer bullet that is sligthly larger in diameter at a slightly higher velocity. It's not a huge differance, but it is worth taking into consideration. I don't know alot about .32 NAA. I hear you can get a 60 gr bullet going 1450 FPS. It is a new and un-tested caliber, so I'd stick with the battle proven 9mm Mak round. I am thinking about getting myself a second Mak and conveting it to .32 NAA just for the heck of it. I'd like to do some testing of my own with this new caliber...
http://www.makarov.com/32naa/index.html
Overall, I've been very happy with my Mak as a carry gun. I have no plans to replace it, and I trust it with my life. I can't believe you can buy a pistol this good for so darn cheap...