I've been through a bunch of tea infusers lately, and after a number of failures, I've finally done more research and have settled on this guy. It's simple - basically foolproof - and easy to use with an open top and a cap to keep things warm or hold the strainer on the counter. And it's not expensive at all.
If you want my second pick, it would be this similar style from FORLIFE Design, which is touch more expensive and has a bit more design love.
And if you just want some fun, I love this Deep Tea Diver Loose Tea Strainer from FRED pictured below.