You're probably looking at an iMac, but it really depends on what kind of resources your development platform needs.
The most economical Mac is the Mac Mini. But you are limited to 2 GB of RAM and your hard drive options, while not small, are also limited. The mini also has a less than stellar graphics card, although it's OK for most regular applications.
The powerhouse is the Mac Pro. You have access to installing multiple processors, multiple hard disks, a large amount of RAM configurations and some graphic card options. The downside is the price; they start at around $2000 USD. The mini's start around $600 USD.
The iMac is a nice middle of the road machine. It has a good graphics card in it's default config, and up to 500 GB in HD space and up to 4 GB RAM. It's starting cost is around $1200 USD.
You can get a fell for each of them by going to Apple's web site at
www.apple.com
