Ok so i had a customer that wanted to block iGoogle but allow google which turns out to be tricky as the only way to tell the difference is by the gadgets and the title bar.
i tried to do some research about iGoogle: every sites of iGoogle what I tested has the same title in html source code. Exactly: iGoogle

So you can use DLP sensor to detect this title in http request and block this sites. I have tested this on a FortiGate-60B with 4.2.3 version of firmware.

I tried to solve this problem over application control, web content filter and FortiGuard web filter but I didnt find solution here.