N8ARY has basic circuit diagrams for building the setup necessary to use an HT with EchoLink. Its pretty basic and simple to do (from the looks of things). I am sure it is something most “hams” could figure out, but its always nice to have something to reference when building yourself. The site is not fancy or galmorous.
If you aren't feeling brave enough to build your own, he will sell you a pre-built one, that is tested to be working.
I personally appreciate it when someone is willing to sell something like this, but also is willing to give you the directions yourself. It implies to me that the person isn't out to just make a quick buck, but is actually trying to encourage and grow the hobby.
Personally, I'll probably try to build one myself, just for the sake of learning . I'll probably also see if I can find more detailed directions elsewhere. In case I can't find other directions, I figured it would be good to share this site with others.