Remote desktop clients for iPhones, iPads, and iPod Touches.
If you want to check out clients for a different OS, go back to the Remote Desktop Clients index.
If you're looking for servers, go to the Remote Desktop Servers index.
Ericom AccessToGo – free mobile RDP Client for iPhone, iPad, and iPod touch
WinRemote – a much cheaper alternative, at $1.99. It also has a free trial available.
WinAdmin – more feature complete and solid than WinRemote, but also more expensive at $11.99