Woohoo go Timbers!
So American stuff? Here is what I would do:
Residential: Powersearch "mattb325" on the SC4 Devotion site, or LEX (thats the shortened name of it.... not really sure who made it up though). The powersearch button is at the top.
Commercial: This one's a little tough, but you do have a lot of choices. For midrises to highrises, I would start on Simtropolis with
Ill Tonsko,
Sparkythepenguin, and
JT Portland. For Sparky and JT, you might recognize a few of those buildings
Industrial: I don't do too much dirty industrial stuff in my cities (that's a good one for marsh to answer) but for farms, try the
SimPeg Agricultural Mod (SPAM)Transportation: I'd look around
BriPizza's site. It's in Japanese, but it has some great "overhanging" stations. That means that you can plop a 1x1 or 1x2 lot and you will see a 3x1 or 4x1 station adjacent to that piece, overhanging a road or even an intersection. It's a little much to handle at first just because it can be used for so much. Use the NWM I liked to above too. None of these lots have dependencies except for the newest ones, which are downloadable right on the site.
By the way, the golden rule of downloading stuff from the biggest sites. They will have these things called "dependencies" or "needed files". You
HAVE to download these, or the buildings and/or the game will act really funny. Once you download one pack once, you won't need to do it again. On the LEX, it will tell you when you have downloaded something but on the STEX, you will have to remember. Watch out though; some packs appear on both sites.
That's a lot of information so I wouldn't be surprised if you have some questions
so please ask in this thread if you do, The people here are here to help you, we love doing it!
Also, if you see in one of our cities something you like, we can tell you where we got it if you ask too.