well, there are lots of programming languages out there, and personally i think that learning to program by programming robots is hard.
if you just want to learn programming (which i recommend, it makes programming robots easier) i would point you towards zends php 101 tutorial, its on php (90% of websites you goto use php) so its useful to know anyway, but php is based on c, which is what the $50 robot is coded in, so yea
i learned php before i ever did robot programming, i think it helped me a lot
heres the tutorial:http://devzone.zend.com/article/627
it's the best programming tutorial i've ever read, but like i said, its intended for web programming, not robot programming, but, the concepts are still there, obviously some of the stuff in it wouldn't be useful to you (i would only look at parts 1-6)
i'm sure someone else probably knows of a good c tutorial, but this is something to get you started.