http://www.doubledutchgames.com/speedrunner
This is the original flash version of Speedrunners. Can we use it? If so, i have found clipping glitches that can save a lot of time over all!
Sadly this is the only in-game timer for minecraft. I as a mac user have just recorded my good runs and timed out the loads by cutting out everything but the gameplay in iMovie. I hope this is helpful. EDIT - Alternatively, there is a statistic that shows minutes/hours played. There is also one that shows tick count and if you take the number of ticks and divide by 20 that is your In-Game time in seconds, just then convert to minutes.
For minecraft there is vanilla and custom maps, due to the large number of custom maps it is hard for us to have our leaderboards on this site. Could there be an ability to make sub sections for games. For Example
Minecraft -Vanilla ---Category -Maps ---Type of map -----Map -------Category -----Map -----Map ---Type of map -----Map ------Category -----Map -----Map ---Type of map -----Map ------Category -----Map -----Map