Thanks for the advice.
I truly enjoy my Arduino. Even though I've only done the blinky tutorials, I've found my programming experience has allowed me to really play around with it regarding how it reacts and making modular code.
So far, I've spent about $300 on parts from Adafruit. The Make book I referred to has the experiment kits for sale for about $100 each (total of two), and then they have the tool kit itself for even more money. Adafruit has a decent kit with solder for about $100. By the time I add shipping (and maybe a few extra small parts) it gets up around $400.
Believe me, most parts are mega-cheaper if you can order them from surplus vendors like I've mentioned; now, you don't say where you're from - from what I understand some surplus dealers won't (or can't?) ship to international addresses. However, if you are located here in the States, you are doing yourself a diservice by not shopping thru them.
I was hoping there would be a good simulation software that teaches the concepts.
Take a look at these packages (I can't vouch one way or another on them; these are just things I found with some googling):http://www.ni.com/multisim/http://www.logicworks4.com/http://www.tina.com/English/tina/
As you can see, such software exists, both in mixed mode and digital-only (and analog-only as well, but I didn't see one off-hand). I would be willing to bet that somewhere out there, you can even find vaccuum tube simulation software, if you look hard enough! At any rate, the above are three packages I found googling on "circuit simulation software teaching"; I'm sure with a bit of effort, you can find more. As I noted before, prices are all over the map (most of the free simulation software you will find will be *nix based; look into the gEDA project for example stuff - note that the stuff is fairly powerful, but very complex to learn).
Guess I'll have to bite the bullet and buy more parts. I will consider the books, but if they're pricey they'll have to wait. If it comes down to books or parts to experiment on, maybe I'll suffer and get the parts first. At least there's info online to look up.
I would stress that if you are serious about this hobby, get the books you can -first-; even if you use simulation software, you will still want and need them to understand what is going on. A copy of Grob's "Basic Electronics", of an older edition, shouldn't be too expensive (a brand-new current edition will run you $100.00+ USD, simply because it is a college level, EE101-course textbook - but a used older edition shouldn't cost more than $25.00, depending on the condition and edition - anything post-1992 or so will have everything you need to know in it). Now, the Mimms book series can be expensive (I think new, each one of the current editions go for about $25.00 USD or so - and there are several volumes), but you can find the small pamphlet-style versions that Radio Shack used to sell in the used and second-hand category (check Ebay, Amazon, Alibris and Abe Books for starters). Depending on who, what, when and condition, you can pick them up for a couple bucks each.
The problem with online information is finding information you can trust to be accurate. Fortunately, you have these forums; you can also be sure of places like Electro-Tech Online forums - but after that, you really need to know at least something about what you are doing in order to know that the information you are reading has merit and value (and won't just cause you to scratch your head while blowing up parts). That isn't to say this forum, any others, or even Grob is perfect, but considering how long Grob's "Basic Electronics" has been published and trusted over the last couple of decades and more, it has that "authority" of accuracy to reccommend it.
Just something to keep in mind.