Sevenval offers a web based emulator.
The incoming markup, including WML, is transcoded into desktop browser HTML and the outgoing request back to a mobile device.
It is possible to use the emulator in each template and website you want.

Windows Mobile sdk's are available for microsft and they even have a standalone emulator that uses your computers internet connection through active sync. It is a little difficult to set up but once you have it done correctly it works really well. You can even down load different device configurations such as full keyboards and vga screens. It is pretty cool.

Can any one guide me how to setup an online Emulator for my site. As I'm a J2ME Game developer I'd like to post my games online on my site and allow users to try those games.

Have you looked the J2ME MicroEmu emulator.

I've never used it but it looks like exactly what you're after. It can be used to demonstrate J2ME apps online in an applet, and there are plenty of examples online on their website

I need a Handset Emulator with a control panel to update the Emulator regularly with new phone hanset models