[dr4g0n]

I've had some good experience with iodine in the past, it's been useful at airports and on trains to bypass captive portals.

It's extremely variable in performance, and can sometimes require a bit of tuning on the client side to work reliably; however, for the most part the auto-detection works well, and will upgrade to raw UDP on port 53 if it is possible.

[userbinator]

The biggest downside with DNS tunneling is the high latency and low bandwidth - many "responsive" web apps feel like molasses, even long static pages take a surprisingly long time to download, and streaming video/audio becomes almost impossible. Of course it's better than no connectivity as a last-resort; SSH sessions are still quite usable and you can do basic things like email and forums.