Well, it's a little late since this was on last night (at least in L.A.), but there's a really cool new PBS show called "Transistorized" that chronicles the development of vacuum tubes, semiconductors, and the lifestyle-altering transistor. I wish I knew about it beforehand, but found it last night just as the show was starting. Hopefully it will repeat or be shown at other times in different cities. It's a very good doc that I think a lot of forum members would find fascinating. So look for it! http://www.pbs.org/transistor/
Check out this old animated clip showing how a tube works! (How 'bout them monkeys!) http://www.pbs.org/transistor/album1/addlbios/deforest.html
I caught part of the show on PBS and thought it was pretty interesting. The show seemed to indicate it was the transistor radio itself that gave rock n' roll its start. Something about kids being able to listen out of earshot of their parents. I thought that was neat. They talked about transistor radios as the first personal communication device of the information age.