Using coding katas is a good way to learn and fine tune TDD/BDD skills. A common way to perform the code katas is in a coding dojo. But a coding dojo involves a lot of people and doing katas on your own might feel a little bit boring. At least I think doing katas alone is boring. So recently I tried out Project Euler. Project Euler is a site where you solve different more or less difficult problems and you solve them any way you like. I've started solving the problems using BDD style specs with the xUnit.net framework. Even though most problems are mathematical in nature I think it is a fun alternative to doing code katas on your own. And you get a chance to dust off a few of the mathematical skills from school that you thought you'd never need again.
If you have a Project Euler account and is logged in you can use this link to view my stats.