Canon EF 70-300mm f/4-5.6 IS USM Lens

This is one of the best non-L series telephoto lenses. Don't compare this with the other cheapie 70-300mm or 75-300mm lenses. It is a major upgrade from the 75-300mm IS that it replaced.

The lens has an ultra-low dispersion lens element (that is normally reserved for the L series). But only has the lesser non-ring USM which means that the autofocus isn't the fastest, and you can't manually override it without switching to manual. But in all it's pretty reasonable.
Although the list price is £400, it's available online for under £350, or on ebay for less (although not a lot less, because it's quite sought after).
Until the end of June 2008, Canon have a £40 rebate on this lens (you must provide the bar-code, and receipt) so double check with your retailer.

It's not too bad for lens flare, but I'd always recommend a lens hood. The ET-65B is a circular hood (because the front element rotates during focusing). But it is a bayonet mount, and will store back-to-front on the lens when not on the camera.

Summary: A good focal length range, reasonable build and optical quality, the IS helps to make up for the slow aperture.