Skillinator is a very useful mod, I just didn't mention it because it isn't what you asked for -- it's neither autonomous nor any more career related than any other skilling mod I've run across. For actual autonomous study there's Inge's Sensible Study Bookcase at
http://www.nectere.net/smf/index.php?topic=116.0 and now that I've found that I can't remember if I've seen others.
Honestly, though, the very nature of autonomous behavior means that your Sims might very well autonomously decide to do something else instead. Rather than trying to convince your Sims to do on their own what you want them to do, it's better to just tell them, and JMP's tools like Skillinator and Macrotastics will let you do so in a way that's still fairly hands-off.