I find it really useful to be able to send commands from an editor window to a terminal, so I've created a plugin for sending text to a Mac Terminal window: github.com/karthikram/Rtools)
If text is selected, it will send the selection to the terminal when you press cmd-Enter; if no text is selected, it will send the current line to the terminal and move the cursor to the next line.
I hope to add the following features in the future:
Allow easy customization of the target program (e.g., iTerm, gnome-terminal, etc)
Work on Linux and Windows
Allow customizing the target program based on the file type
I hope this will be useful to others. I presently don't have a Linux or Windows machine to work on, and I'm not sure how to send text to programs in Linux or Windows. If you know how to do these things, please feel free to fork the repo and submit pull requests adding these features.