The Apple iPhone 3G Dock is a $30 dock sold by Apple. I use it at my office every day, throughout the day, and there is a lot to love about this simple little dock. First, it gives me a specific place to keep my iPhone when I am working at my desk so that it is always in that same convenient location when I need to reach for it. Second, it keeps my iPhone charged while it is sitting in the dock. You can connect the dock to your computer to charge and sync, but I don't actually use that feature because I don't sync my iPhone with my work computer; I sync with my home iMac where I keep my music, photos and videos. To send a charge to the dock, I connect an iPhone connector cord from the back of the dock to a USB power plug. The dock does not come with a connector cord or a power plug, so you'll either need to use the ones that came with your iPhone or buy an extra dock connector cable for $20 and an extra USB power adapter for $30 if you want to buy from Apple. (Amazon sells some cheaper alternatives.) I also found that the cable was not long enough to reach a power supply on the floor next to my desk, so I added a USB extension cable which you can buy at places like Amazon for just a few dollars.
Third, I like the dock because it keeps my iPhone upright and visible. A quick tap on one of the iPhone's buttons shows you the time, date and a battery indicator showing how charged it is. Or you can keep the iPhone turned on and display a photograph (a single one or a slideshow), an iPhone app, or whatever else you want. Note that your iPhone will auto-lock after a short amount of time unless you turn that feature off in Settings --> General --> Auto-Lock. The dock itself is weighted just the right amount so that it will not fall over when your iPhone is in it, and rubber on the bottom gives you good traction so that it does not slip on your desk.
If you want to be more creative, there are lots of sites with tips for other ways to create a dock for your iPhone. For example, click here for a YouTube video showing you how to turn a simple paper clip into a stand for your iPhone, and there is even a PDF file you can download so that you know exactly where to bend the paperclip to make the stand. This sounds like a joke, but I tried it and it actually works quite well. While the Apple iPhone 3G Dock keeps my iPhone in a portrait position, I sometimes put my iPhone on the paperclip stand to put the iPhone in a landscape position to display a video or just show a slideshow of pictures on my iPhone (the vast majority of which are wider than they are tall so landscape mode works better).
Going from the strangely useful to the increasingly absurd, this site shows you how to make an iPhone dock out of cardboard, and this video shows you how to create an iPhone stand out of a $100 bill. I suppose you could do the same thing with a $1 bill to show your clients your frugality. Ahem.
There are also some other companies that sell iPhone docks that might work for you on your desk. Amazon sells quite a few of them and they differ from the Apple dock in different ways: some are cheaper, some come with a connector cable, some add extra features such as a media card reader. One interesting choice is the Griffin Powerdock Dual-Position Charging Station for iPod and iPhone which lets you charge two iPhones (or an iPhone and an iPod) at the same time. Another interesting choice is the PED3 Rotating Dock Stand that makes your iPhone look like a little computer monitor:
But back to the Apple dock, it is simple, sleek and works very well and I can recommend it. It is somewhat overpriced, especially considering that it doesn't come with a dock connector cable or a USB power plug, but it works well. If you use it every day like I do, it is worth it. Here are a few pictures, and you can click to view larger versions: