I seem to know how to make a tile-able/repeat pattern in Photoshop easily enough, but I'm wondering if there are any great tools available specifically for pattern tile design. It would be a great feature to be able to see how the pattern tiles as I edit it.
This might not be the answer you were looking for, but it might be useful anyway.
Any search for tile background generator will give you more alternatives than you can shake a stick at.
You are not telling us what use you want; is this CSS pattern? General graphics? So here are a list of just a few online tools.
If what you are looking for is a plugin for photoshop, I am sure someone else will come along shortly with suggestions.