How can I hook into an entityform submission? I've got entity forms installed, and I'd like to use some db_queries when a particular entity form is submitted, as to make use of the information filled out on that entity form.

Is this possible, and which hook should I use?
If I understand your question right, you should use the following hook to capture a submission:

hook_entityform_insert($entityform)


As described in the comments at the top of entityform.api.php:

* Entityform and Entityform type are standard entities using the Entity API module.
* The standard Entity hooks are availabe for them.
* Including
*  ...
*  hook_entityform_insert


Hope this helps

Addition:

here is the sample code I used:

function mymodule_entityform_insert($entityform){
  dsm($entityform);
}


and it did get triggered as soon as I submitted an EntityForm.