I recently came across a whole stash of free TOEFL test practice materials at this link.
I only really had time to check out some of the speaking tests. The positive is that the creator of this site has managed to very accurately replicate the actual TOEFL test browser format, including the automatic timer function (so it will be good for you in terms of getting a great feel for the actual test experience.
On the negative side, many of the actual recordings for the listening sections come out quite muted and difficult to hear without turning your volume settings up ultra high. Even then, it's distracting because the narration sections are clear and set at a higher volume - so one minute you'll be straining to hear the speakers in a dialogue, and then the narrator will come on and blast your eardrums out! Also, despite the great timing functions, you can't actually record your performance or listen to yourself afterwards.
Still, as I said, it can still be great practice, on account of the close resemblance to the actual TOEFL browser and automatic timing functions. There are also a lot of tests and practice items to go through, including all the other parts of the test (reading, listening and writing as well as speaking).
One note of caution: I don't know how long these materials can/will stay available up on the web. The site maker has not documented where the original materials came from - so there is a good chance they have been burned, copied and uploaded illegally using some other source. Maybe (hopefully) I'm wrong there, but generally speaking I would expect to see rights/copyright asserted if the site owner had made or organized the making of all these materials privately...