This grain and hops strainer is perfect for me and my setup because it can be added and removed from my brew kettle very easily.
3 inch PVC collar - $3
2 pack 5 gallon nylon paint strainer bags - $4
Hose clamp big enough to fit collar - $1
3/4 inch dowel $2
Drill or drill press
7/8 spade bit
Step 1: Not Much to It
And you're pretty much done. To assemble just slip the bag around the collar and tighten the hose clamp securely around the bag. The dowel rod will hold the bag over your brew kettle kind of like an over-sized tea bag.
Step 2: Plan Your Next Brew Day
Once the bag is actually over the kettle, about the only thing I would recommend is to give the hose clamp an extra turn with the screwdriver a few minutes in. You definitely don't want to loose your bag in a kettle of boiling wort.