For a capable low-cost mill, the Lathemaster ZAY7045FG is not bad. Users generally seem to be pleased.
http://www.lathemaster.com/MILLINGPRODUCTS.htm
Avoid round column mills.
The largest of the smaller Harbor Freight and Grizzly square-column mills aren't bad, and there's a ton of hobbyists out there if you need help. It is also relatively easy to retrofit as a CNC machine. They are supposedly made by the same company.
http://www.grizzly.com/products/G0463
Some people like this one, though quality can vary:
http://www.grizzly.com/products/G3102
That said, I've decided I want quality and am finally looking at an Abene vertical/horizontal mill. I found a really good one for $4,500. and have a chance at another like it for just over $100, though it is missing the horizontal mill support arm. I may get it as a spare. These mills weigh around 2,800 pounds and make a Bridgeport look wimpy. The spindle motor is 6 HP and it supposedly has a built-in has anti-backlash mechanism so climbing cuts shouldn't be a problem. They have 3-axis power feed, too.
If you can get an old but good mill such as Gorton, Wells-Index, Cincinnati or the like you'll have something that will last. Bridgeports tend to be light and often get abused.