I'm really enjoying Tom Jones' astronaut memoir Sky Walking, though it's taking me a while to finish due to various interruptions. I'm now reading the part in which Jones is preparing for his fourth mission, STS-98 on Atlantis in February 2001. This ISS assembly mission (5A, the US Destiny Laboratory Module) was delayed from spring 2000 due to other delays, mainly that of the essential Russian "service module" (Zvezda) which was planned for 1999 but didn't actually launch until July 2000 (this article on the ISS assembly sequence is very handy). With all the problems in Russia at the time, it's a wonder the ISS project ever got started.
The delays gave Jones and the other early ISS assembly astronauts a lot of time to train (often under water) for the complex EVA's and robot arm procedures that would be needed to assemble the ISS in orbit. Of course there have now been many of these assembly missions, and while they are still not easy missions to plan and execute, there is a lot of experience to build on. In 1999-2001, there was not much experience in orbital assembly, despite such impressive EVA accomplishments as the Hubble service missions in 1993, 1997, and 1999. Jones was also the deputy chief of the Space Station Operations Branch for several years before his mission, so he was really immersed (literally and figuratively) in space station issues for a long time. It was a complex and often frustrating situation on many levels.
All of this discussion (and trying to visualize some of the assembly problems he discusses) made me realize that I don't really know that much about the ISS. I'm familiar with the overall structure and have a vague idea of the various modules. I've seen pictures and even some Orbiter models of past and future stages of the ISS. So I took a quick look to see what sorts of "ISS for dummies" material might be around.
The diagram above is from NASA, but I couldn't find this August 2007 (post-STS-118) version except in Wikipedia. The color-coded exploded view gives a pretty good idea of what's what. For a better idea of how everything goes together, this animation from Tietronix (sample frame at left, made for NASA but I couldn't find it on any NASA sites) is the best demonstration of the assembly sequence that I've seen. For ISS operations and a virtual tour, this Interactive Space Station Reference Guide is pretty good. Of course the main NASA ISS page has a link to this and many other ISS related articles and features. I'm sure there are many other good resources, but these can give you a good start in better understanding the ISS.
Now that I think about it, one of the best things I've found for space flight background and ISS information is a book I wrote about in fall 2006, Space Station Science by Marianne Dyson (second edition, 2004). Although aimed nominally at ages 9-12, it's really good for anyone with an interest in the ISS. It may be time for me to read it again.
P.S. Another great resource is NASA's Reference Guide to the International Space Station. Dated August 2006, it's divided into 10 PDF files, several of them quite huge due to the large number of detailed color graphics. The total download is about 76 MB.