You really don't need Xenon CPU's for graphic design. The Mac Pro is way overkill.
If you already have a good display, the Mac minis were just refreshed with new Sandy Bridge i5's and i7's, and the high-end ones (which can still come in under $1k) finally have a discrete graphics card. The memory is easily upgradeable, too. The client models have dual-core i5's upgradeable to an i7 in the high-end. There is a server configuration with a quad-core i7 and dual hard drives, but you sacrifice the discrete AMD GPU. It is possible to add a second hard drive to the client model on your own, but this will void your warranty if anything goes wrong. One important thing to note with the new Mac minis is they have no optical drive, so you'll need another computer or the add-on USB DVD drive if you need to work with optical media. The Apple store probably has refurbished old models that still have the optical drive, but the hardware of the old Mac mini was rather anemic compared to the new ones, so I wouldn't do that.
If you don't have a good display, the iMacs are a pretty good deal despite being all-in-one desktops suffering from can't-upgrade-itis, since you're getting a very nice display on them (though it is glossy). If you get the 27-inch, you're essentially getting a $999 display that just happens to house a computer in it. I believe you can upgrade the memory on your own, but make sure to configure the hard drives you'll before ordering, as you can't upgrade the drives without disassembling the whole thing and voiding your warranty, a major headache.
If you want to work on the go, the MacBook Pros are still a good deal, having been refreshed in the spring. Both the 13-inch and 15-inch are very portable. The 13-inch is lacking in resolution, being only 1280x800, so you'll almost definitely want an external display for graphics work. The 15-inch's display can be upgraded to a respectable 1680x1050 from the default 1440x900. You should also consider the hi-res (1680x1050) matte display option over the standard glossy display if you go this route, for more accurate color and less glare. The MacBook Pros can take up 16 GB memory if you can manage to find 8 GB sticks, but since those are pretty rare and expensive, you'll probably just want to upgrade to 8 GB (cheaper if you get it elsewhere). Besides the display, the other primary difference between the 13-inch and the larger models is the 13-inch only comes with Intel HD 3000 integrated graphics, while the 15-inch and 17-inch also come with discrete AMD Radeon GPUs, which will definitely help for graphics work and driving extra monitors. Also the 13-inch is only dual-core, while the 15-inch and 17-inch are quad-core. That may help with rendering and stuff, but I'm not sure how multithreaded the Adobe suite is.
I don't know how large your budget is, but there is also the possibility of an SSD to consider over an HDD, which would definitely help when working on large files that use a lot of scratch disk space. The downside is, of course, they're much more expensive and not as large. On the higher-end iMacs, you could configure a model with both a 1-2 TB HDD for storage and a 256 GB SSD for your apps and scratch space. One thing to keep in mind with the MacBook Pro, where you could upgrade to an SSD later if you want, is Apple only supports TRIM (this is a system command that keeps the SSD from slowing down over time) on their own drives, not third party ones, so if you decide to upgrade to an SSD later, you'll want one that makes up for this with firmware on the drive itself, like a SandForce SSD.
As Lisa mentioned, the refurb store can have good deals if money is tight. They're covered by the same warranty as new Macs. Sometimes they have current-generation Macs, and sometimes older-generation Macs, so make sure you look at which generation (it'll list the date of release on the store) you're getting and what its specs are. If it's an iMac, make sure the hard drive is big enough for you, since you mysteriously can't upgrade it.
Well... that's a lot to read. Feel free to ask about anything I've mentioned.