Pretty much what Paul said.
In terms of brands, pretty much any well known camera manufacturer will do. Canon, Olympus, Nikon, Leica, and more recently Sony and Panasonic. If buying a pocket camera, make sure it has a macro setting (ie. small tulip icon).
Like Paul said, a DSLR may be overkill for online stuff, if that is all you plan to use the camera for. Personally I own both an Olympus DSLR with a macro lens, and a smaller Leica pocket cam. I find myself using the Leica more often as it is often handier when I just need to snap some quick photos and post online. Remember: It is entirely possible to shoot crappy photos with an expensive camera if you don't know what you are doing, just like you can make good pictures with a cheap/old camera, if you know it well.
It is rare that I bother setting up a proper light rig, so often I just shoot the minis using flash - usually a big nono in miniature photography, but knowing how the flash lights up the image frame I can place the miniatures accordingly and usually get decent results, good enough for online use.
Go DSLR if you plan to photograph a lot in general. Especially outdoors stuff with plenty of detail as the image quality is superb due to the extra light through larger lenses, and larger image sensors of DSLRs. If you know what you're doing, the manual features of a DSLR also gives you a lot more creative freedom. Personally I rarely ever use the automated settings on mine, as I've come to know my camera well.
A pocket camera has the advantage of being compact. It is more usefull for carrying with you to parties and stuff where you wouldn't normally be dragging a bulky and expensive DSLR with you. Remember: The best camera is the one you always carry with you, to capture those special moments. A pocket camera is also quite adequate for most online work when it comes to miniature photograpny.
But as Paul said: The key feature is setting up good lighting. Ideally you'd want at least two lights (3 if you feel ambitious) to cancel out any shadows on the miniature. You'd also need a good backdrop that reflects light back on the miniature, but doesn't upset your camera's light metering and white balance too much: Too dark background and your miniature becomes over-exposed. Entirely white, and your miniatures become too dark. Lighter backgrounds are better though, as you can salvage a dark photo in an image editing program. This is not possible with an overexposed photo. Ideally you want a background that is the equivalent of 50% gray. But technically it can be any color (Imagine if you had a blue background and photographed in black/white: The grey color you'd get should be roughly 50% gray).
You can print your own background.The blue to white gradient backgrounds you see in many miniature photograps aren't necessarily digitally additions. The gradient works a bit like the horizon on a landscape image, and makes it easier for the camera to automatically select the proper exposure and color settings.
That said, you'd usually want to go back and edit your images a bit afterwards. It is usually necessary to adjust the brightness and color balance slightly, and you'd need to crop and compress the images for online use anyway. 150kb is a good standard size to aim for. I tend to compress to about 60% which keeps the image quality fairly good. Personally I like large images, but bear in mind what can actually be displayed on screen in a browser. There's no reason to make an image more than 1500 pixels wide (Well unless your're making an army shot and want people to be able to zoom in on every model
)
edit: Oh, and a word on the miniatures themselves: Remember there's a difference between what you THINK you see, and what you actually see. When you've spent time painting a miniature you know the shapes and color very well and have formed a mental image of it in your mind. This means that you sometimes become blind to what sort of photos you actually take of the piece. You know what it is supposed to look like, so your mind makes up for the information you cannot see in the picture. But to an outside viewer this is not clear at all. (We are in fact very reliant on what we EXPECT to see, and do not very often actually look at things. If I paint a potato blue with some red, yellow and white on it, you'll have no idea what it is, untill I tell you it is supposed to be an Ultramarine, but after that, all you will see is a (somewhat amorphous) member of the Adeptus Astartes).
It doesn't make it any easier that your eyesight is stereoscopic, and the camera is not. Take your time and find the best angle for the shot, that gives the best imperssion of the shape. Sometimes it is only a few degrees that makes all the difference. Of course there are times when you need more images to really do a miniature justice. But the point is, that even if you know that a miniature looks good, it may be poorly recieved if you photograph it from a poor angle. And of course: Choosing a dramatic angle, that really captures the essence of a miniautre will really bring it to life!
