 <p>If your interests are machine learning, data mining and computer vision then I'd say a Lego mindstorms is not the best option for you. Not unless you are also interested in robotics/electronics.</p> <ul> <li>Do do interesting machine learning you only need a computer and a problem to solve. Think <a href="http://aichallenge.org/">ai-contest</a> or <a href="http://mlcomp.org/">mlcomp</a> or similar.</li> <li>Do do interesting data mining you need a computer, a lot of data and a question to answer. If you have an internet connection the amount of data you can get at is only limited by your bandwidth. Think <a href="http://www.netflixprize.com/">netflix prize</a>, try your hand at collecting and interpreting data from wherever. If you are learning, <a href="http://www.autonlab.org/tutorials/">this is a nice place to start</a>.</li> <li>As for computer vision: All you need is a computer and images. Depending on the type of problem you find interesting you could do some processing of <a href="http://www.opentopia.com/hiddencam.php">random webcam images</a>, take all you holiday photo's and try to detect <a href="https://en.wikipedia.org/wiki/Face_detection">where all your travel companions are</a> in them. If you have a webcam your options are endless.</li> </ul> <p>Lego mindstorms allows you to combine machine learning and computer vision. I'm not sure where the datamining would come in, and you will spend (waste?) time on the robotics/electronics side of things, which you don't list as one of your passions. </p>