I just realized as I was posting this that Steve Smith said essentially the same thing. Sorry for the redundancy, but that means two recommendations on the "L" from the refurbished store.
If you are in the U.S.: ACT RIGHT NOW. The Canon Refurbished Store is having their 20% off sale and the 70-300 L is just over $1,000. http://shop.usa.canon.com/webapp/wcs/stores/servlet/product_10051_10051_327247_-1?WT.mc_id=C126149
You might even get free shipping with Coupon Code; SHIP712 (see CanonPriceWatch.com). This is a fantastic lens and if you can swing it, buy it.
Now, if you absolutely cannot afford the "L" lens, I would honestly recommend going a cheap route and picking up the new Tamron 70-300 stabilized lens. It is less expensive than the Canon IS lens, but from all accounts it is sharper. I had that lens before I gave in to the desire for the "L." Don't get me wrong, the "L" lens is much better (sharper, weathersealed, built like a tank, etc.) but I really had few complaints about the Tamron. It was as sharp or sharper than the 55-250 mm lens, which is actually quite sharp (although not USM and lacks build quality). I don't have any experience with the 70-300 non "L" IS lens, but from reviews, etc. it doesn't seem to be a stellar performer and is more expensive than the Tamron.
Only problem I ever had with the Tamron was an occasional hangup when it would hunt for a focus point. Although I honestly don't know if that was a problem with the lens or with the 7D center focus point not being able to focus on a subject due to contrast issues.
Anyway, that's my two-cents.