Actually, you can just use a single term session. Just kick off bitcoind in the background:
bitcoind &
(see http://unix.stackexchange.com/questions/103731/run-a-command-without-making-me-wait for a little more detail)
nohup bitcoind &
If you built from source, you can run:
sudo make install
This will copy the relevant executables into a systemwide accessible location that is already in a user's path by default. Of course, you could certainly do as you mentioned and export $PATH to include the path to the binaries in the src directory from the build.
Indeed, make install definitely seems like the more normal thing to do. OP didn't comment on why he didn't run make install and I just thought I'd follow up on the question about why the "./" (because what you're trying to run isn't on your $PATH).