Dangerous When Wet with Esther Williams features a swimming race across the English Channel. She also starred in Million Dollar Mermaid, loose biopic of Annette Kellerman, who set records in distance swimming and was also a professional high diver and stunt swimming artiste (described here as the fore-runner to synchronized swimming)
The closest thing I found for Motocross is A Warm December w/Sidney Poitier.
The Skating Movie Database lists nothing for speed skating (outside of a couple random shots in films already listed)
You should all hang your heads in shame…
The Replacements? North Dallas Forty (OK, this one’s actually good)? How can you guys discuss football movies and not mention BRIAN’S SONG?!?!? (And no, I don’t care if it’s a TV movie)
I believe that by law in 34 states, it is the only movie that men are allowed to cry over. 
We should also mention, in the “good football movie” category:
The Longest Yard
In the “pretty good” category:
Paper Lion
Knute Rockne, All-American (famous for Reagan as Gipper)
Rudy
All The Right Moves
Everybody’s All-American
Remember The Titans
In the not-so-good football movie category:
The Waterboy
Any Given Sunday
Necessary Roughness
Heaven Can Wait (sorta…Warren Beatty plays a Rams QB)
The Best of Times
Wildcats
Johnny Be Good
The Program
Varsity Blues
The Last Boy Scout (sorta)
Also…does the end of MAS*H qualify it as a football movie? What about Jerry Maguire?
Ethilrist:
Does the character of Erich Kreigler in For Your Eyes Only count?