There's plenty!!!!!

The choice depends mostly in the devices you are targeting, or if you want
your site to work on most devices, you'll have to download a few.

For starters you can use the Pocket IE loaded in the Win CE emulator of VS
2003, it's very good if your principal target is Pocket PC's.

A must for every Mobile Web Forms developer it's the OpenWave Emulator,
available here:
http://developer.openwave.com/dvl/tools_and_sdk/openwave_mobile_sdk/phone_simulator/
(Requires free registration).

Then you have to download Nokia's Mobile Internet Toolkit (NMIT) to
guarantee compatibility with #1 vendor of mobile terminals in the world.
You can download it here:
http://www.forum.nokia.com/main/0,6566,034-13,00.html (requires free
registration too).

There's also a very popular online emulator called Gelon
(http://www.gelon.net/), it's very good, but it requires you to have your
pages on a server.

And last, but certainly not least you can use windows (IE) like emulators
like WinWAP or Klondike, they are very good and give you a lot of tools for
development, but pages look cooler in a phone-like emulator!!!!

WinWAP: http://www.winwap.org/winwap/download.shtml
Klondike: http://www.apachesoftware.com/download.html

OK, those are my favorite, hope you enjoy them, Happy testing!!!!!!

--

Juan David Gomez A.
Microsoft Certified Professional
Analista de Desarrollo - PSL S.A.
Web and Wireless Banking
Medellin - Colombia