Most frequently used zooms (on 7D/crop sensor) for sports/action shooting...
70-200/2.8... and 24-70/2.8 a distant second place (someone shooting more indoors might find more frequent need for it). I use Canon, which are fast and accurate focusing, too. I don't know if 3rd party lenses can match them.
Need larger than f2.8 aperture? Go with primes instead of zooms. 28/1.8, 50/1.4, 85/1.8, 100/2 and 135/2 are all useful for sports, thanks to fast and accurate USM focus. I have wider lenses in my camera bag, but they rarely see much use when shooting sports.
A really large aperture isn't always the answer, though. There's a practical limite beyond which you start to run into problems where the largest apertures are a bit soft, or render too shallow depth of field, demand very high precision focusing (and focus slower to achieve that). Not to mention that extremely large aperture lenses are pricey, and can be big and heavy.
Learn to use higher ISOs. With 7D you should easily be able to use ISO 1600. 3200 and 6400 are usable too, though some extra post-processing is likely to be needed. Look for Teamspeed's posts here on POTN about high ISO shooting with 7D. It boils down to three things: 1. Avoid underexposure like the plaque... it is better to slightly overexpose and have to pull back an image, than to have to increase exposure in post-processing. And, 2. Get and learn to use a noise reduction software. It's extra work, but makes higher ISOs usable. Finally, 3. Shoot RAWs, which are far more adjustable in post-processing than JPEGs.