post and this link on RPGNow, at this moment, the entire selection of books is on sale. Timemaster, which is currently owned by Goblinoid Games, is a time travelling game from the past millenium -- with all kinds of awesome!
Even if you don't have any interest in the game system or setting itself, if you have any interest in Time Travel games you should pick up Timetricks. It has a number of time-related difficulties for time traveler on a mission including Significance Waves, getting caught in a Time Loop, and so on.
You can come up with your own mechanics to resolve these issues, but the conceits and their explanations are fresh and fairly unused in my experience with time travel games -- possibly because most time travel games focus on resolving matters in-stream rather than with a constant option to travel back or forward in time.