I've just tried ePrint, which has some limitations, but gets the job done without any print servers. There are two versions of the app: The free version, ePrint Free [iTunes link] lets you print contacts, notes (more on that later), photo albums, and even brings up the camera so you can fire off a snapshot and print it immediately. The paid version [iTunes link], meanwhile, is U.S. $2.99 and adds the ability to print web pages as well
Setting up is easy. The app will find your printers in a snap if your phone is in Wi-Fi mode, and you are running Bonjour zero configuration setup on your network. You can also elect to enter the IP addresses of your printers as well. If your printer is color, and you send color images, you'll get them in color.
There are a few catches, however. To print a web page you either have to enter a URL for it in ePrint, or set a preference to bring up the last web page viewed. When you go to print notes in either app, it doesn't mean from your Notes app. ePrint can only print from the ePrint Notes app, although you can still copy and paste any text into it and print away. That's how I test-printed an email, because Apple doesn't allow any way to print an email or anything else directly. After doing a 'select all' on an email, I copied and pasted it into the ePrint Notes app, and it worked just fine.
In my testing, the app found both my printers, a Brother laser printer and an Epson 2200 inkjet, in a couple of seconds and I was ready to go. If you are in an office environment with Bonjour printing, you should be able to print from most printers easily. The company maintains a support page with some more info and some videos here.
I've found both ePrint apps quite handy, and you can run it on either the iPod touch or the iPhone. If you want to make sure your printer works with them, try the free one first. It may meet your needs by itself, and if you want to print web pages as well, you'll know whether or not the paid version is worth the 3 bucks.