What's a good lens and flash to shoot football games from the sidelines with a

[Penn]

Canon 20D? I am a public teacher on a budget. I have the stock lens that came with it and the built-in flash.

 

[Grant]

IMHO the best all-around lens is the 70-200 f2.8 IS followed by the 70-200 f2.8 non-IS. If you start out with daytime games you can get by with "cheaper" 70-300 f4-5.6 lenses. Skip the flash you don't want to "blind" your players and lose the game.

 

[Foggy Idea]

The Canon 70-200mm f/2.8L would be ideal but at the higher cost, you may want to consider the somewhat slower Canon 70-200mm f/4 lens and for a flash the Canon Speedlite 430EX..