The Rasperry Requiem brown ale is another good thread to check out on various methods of brewing with fruit.
I just brewed this and added 3 lbs of frozen raspberries to a grain bag when I put it in the carboy in secondary. I basically used a cut open milk jug for the funnel to add the raspberries to the grain bag inside the carboy.
Using the grain bag left no haze in the beer, but there is some sediment. I would consider fermenting primary in a plastic bucket then adding the raspberries and moving to secondary afterwards or cold crashing to reduce the sediment next time.
This beer came out awesome and the raspberry flavor is increasing as it sits around. Trying to hold off on plowing thru this since it would be effective with ladies. Now I need to find one of those, but that's another issue.