Hmm. If that's your goal, then you might try it in two stages...for the algorithms side of things, I'd highly suggest looking at some of the programming challenges out there, and do it in conjunction with reading Skeina's book Programming Challenges. It provides a great deal of theory about how to approach problems from an algorithms and data structure point of view, and then points you to a bunch of sample questions where you can try to put these ideas into action on your own. It will very definitely put you through the mental wringer, in a very good way. Very similar to Project Euler, but for hard-core algorithms and data-structures people, rather than math people.
For just the "learning the language enough to feel like you can really use it", well, there are a lot of ideas for that...for me, just to use an example, I like to build a database driven website. Forces me to do a lot of things that you're going to have to do to get into a language in some breadth/depth.
If you need a specific example of a site, and really want to be pushed to do something real, you could contact a few charities that you are fond of, and see who needs a website or other application done for them for free. You're forced to learn, and have a reason to do so in a reasonable timeframe, and they get a useful app for free. Win-win.
