TeamRemind.com is brought to you by SALEient. SALEient develops web applications that don't suck.
The original version of TeamRemind was to help a couple people manage a slow pitch softball team. We wrote the original code in a few hours and the idea was hatched. At first, people didn't use it but after a few key features were added the team of 20 or so people started to actually enjoy it and it became a big part of our season.
After gathering some feedback from some of the people on that team, the plan became to create TeamRemind.com as a bigger, badder version of the original for use by anyone in the world. While there are many competitors for this kind of service out there, they aren't obvious. There are lots of sites that allow you to create a group, send emails and have a calendar but amazingly enough, there aren't any dedicated to sports teams.
That's what TeamRemind.com is for.