My Canon 17-55 F2.8 IS lens had accumulated a bit of dust on the inside of the front element. I came across
this pictorial guide to removing the front lens element for cleaning on
here and decided to give it a go.
Simple as anything. Took about 10 minutes. As the guy says, the dust is lurking behind the front lens element. Removal of the seal is very easy (and looks like where the dust gets in), and as long as you have a decent mini-screwdriver, the screws come out very easily too.
The front lens element then falls out as you tip the lens into your palm (covered in a lens cloth in my case), and you can then clean off the inner surface, and blow the dust off the inside of the lens body.
Result!
All back together and still working in 10 mins. Top stuff.
Now to get a 77mm UV filter or such like to stop the dust getting in again.
Tobers