I use my 40D for youth basketball as well. It's that or the old 300D and that ain't happening.
Anyhow, I use full manual. I'm using strobes so I can get away with a much lower ISO than you shooting ambient. Anyhow, ISO 640 to 1000 has been my range so far with my different light and lens set ups. SS 250 (max flash sync) and f/2.2 to 5.6 depending on which lens was used.
My first attempt at shooting BB was with the 50mm f/1.8. The fantastic-plastic machine wasn't that great. I got some fairly decent keepers, but most were not great.
First atempts with the 50mm f/1.8 lens
Then I rented a 50mm f/1.4. A faster USM lens, but again not great. Even though the f/1.4 50 is a USM it still wasn't up to the speed of the kids. Not so many keepers.
Second lens I tried, the 50mm f/1.4 USM, I had a lot of back focusing issue with this lens.
So then I pumped up my total light output and went with my 70-200 f/4L. This lens is really fast to the focus, tracks well and is super sharp. It's just not the f/2.8 version so it needs a lot more light. I also pumped up the ISO. I switched between ISO 800 and 1000. I found that if I shot at around f/4 to f/4.5 I could go with ISO 800, but the next step to f/5.6 needed ISO 1000. Also, the 70-200 on the 40D is a little long and I needed to shoot from the corners and I found I was limited to only a few different shots. That lens length needs a bit or room on the crop bodies. Not that it's bad, I got a lot of keepers with that lens, but I like the under the basket action better.
70-200 f/4L use here, a much better sports lens, it just needs a lot of light for indoor use.
Now I have a 24-70 f/2.8L and I am hoping to lock down ISO 800, SS 1/250 and f/2.8 to f/3.5 and be able to sit in and around the key behind the baseline. I'll test it out tmorrow night at my boy's practice, then shoot for real in a back to back double header set of games.