Are there any alternatives to using Gamespy Arcade?

Yes. Have a look at The All-Seeing Eye (ASE), which now supports OFP: Resistance as well, and at Hyperlobby. You could also use OFP's multiplayer interface to directly connect to an OFP server game, if you know the server's IP address. Some server hosts publicize their IP addresses on Codemaster's OFP chat page.

If you want to host an OFP MP server and your IP address is dynamic because you're behind a gateway, proxy server or firewall, consider using the WINIP utility, available for free from Algenta Technologies. Winip allows internet users to access your computer via a static host name (e.g. even though you may have a dynamic IP address. This lets others access your computer the same way every time, instead of having to enter a different IP address every time you reconnect to the internet.