There are 3 online “leagues” to sign up for. A national and a local XC contest, and a local Competition League for racing declared tasks. The XC Contests score flights based on points per kilometer, with additional weight given to courses other the straight downwind. These contest are open distance XC. You decide where you are going to go, and the website scores you. Make sure to upload flights within 14 days of flying them. Otherwise XCContest wont score your flight. The instructions link for the US wide contest is here
It costs $5
2nd is the RMHPA League also on XCContest. This is just for local pilots and does not seem to cost anything.
Last is XC Demon. This is for the Colorado XC League. These are declared tasks with turnpoints, and radii. I am eager to try and blaze some of these tasks, and I am hoping more pilots will join me.
Create an account and upload flights after you fly the task.