When you don't have an SSL-VPN or IPSec VPN already set up, SSH tunnels will do the job -- and they just work. SSH Tunnel requires root access, but it allows you to tunnel just about any app through the SSH tunnel to your destination, such as a Linux machine at work. You could point your app at 127.0.0.1 port 12000 and pop out from the Linux box to hit your IIS-based WebDAV server at 10.51.0.200 on port 80, for example. If this sounded Greek to you, just search "how to ssh tunnels" on Google. It's a bit convoluted, but it's worth learning.

Price: Free

Developer: Max Lv

Compatibility: Android 1.6 and up