Hello there fellow Tennis Lovers,
I'm the organizer for Toronto and GTA Tennis Meetup group and creator of TennisChart.com - a free website designed to maintain players dynamic NTRP ratings; meaning that after you assesed yourself for the first time, your rating becomes dynamic and will change after each subsequent game. This way I accomplished to have more competitive matches between players and let them monitor their individual progress over time. And of course I've implemented a whole bunch of handy tools to schedule, communicate, keep statistics and enter scores online.
Feel free to check it out. I know for a fact that this is what everyone wanted for a while now, and I've finally done it.
Thanks and please let me know how you like it.