ColEm is a free application that lets you emulate the ColecoVision, which was part of the first wave of games consoles.
fMSX allows you to emulate the 8-bit MSX range of home computers, and is completely free. The MSX didn't do that well in the West, but it was very popular in Japan, and many famous Japanese game series such as Metal Gear and Dragon Quest were originally written for MSX.
Frodo allows you to emulate the C64, the best-selling 8-bit computer of all time. It's free, and you can download it from the author's website.
iNES lets you emulate the Nintendo Entertainment System (also known as the Famicom in Japan).
Jackpot Casino contains six mini-games with a casino theme: Black Jack, Roulette, Slot Machines (aka One-Armed Bandits), Caribbean Poker, Video Poker and Craps.
MasterGear lets you emulate Sega's classic 8-bit consoles, the portable Game Gear and home-based Master System, all from the comfort of your N-Gage-compatible phone.
A roulette table simulator with online features including chatting to other players and watching as they place their bets too.
A fruit machine / one-armed bandit simulator with the added novelty of being able to chat to other players through the internet.
S60-CPC (which is still very much in the experimental stages!) is a free application which lets you emulate the Amstrad CPC range of home computers including the 464, 664 and 6128.
Speccy lets you emulate the Sinclair ZX Spectrum, Britain's best-selling home computer. It had over 10,000 games released for it in its lifetime, and gave birth to many famous names including Rare and Codemasters.
Virtual GameBoy lets you emulate the Game Boy and Game Boy Color on your N-Gage-compatible device.
vSun lets you emulate the Super Nintendo Entertainment System on your N-Gage-compatible phone.