I just bought my house in April, so I'm starting small and will move around equipment/upgrade in a few years.
There's the living room, REC room, and basement home theater.
In the Living Room, my receiver is an RCA piece of junk I got from Target back before I was in college (whole 5.1 system). It has a passive sub with it as well. The speakers are useless, so they're in a box somewhere. Fronts are Pioneer SP-FS52s, center is a Pioneer SP-C22 (coming in on Friday), and the rears are old garbage KLHs that will be replaced with the BS22s once they go on sale again. Surprisingly, it doesn't sound half bad...I added a Sony SA-W2500, since I got it for cheap, and with that and the stock RCA sub, it does the job well enough for now. I'll probably upgrade the receiver within the next year...but the speakers are high enough quality to keep me happy for a while. Mostly casual TV watching and music listening in this room.
Fortunately the REC room had speakers installed in the ceiling already. They're garbage, but good enough for now...no clue what brand/model...not worth looking at anyway. They're being powered by an Onkyo HT R510. Typically just plug my phone in for some tunes while shooting pool.
The movie room is set up with 7.1. All 7 speakers built into the wall...no clue what brand/model, but they sound excellent for action movies and mediocre-to-good for listening to music. The sub is an old powered Kenwood that I got for free...it's loud as hell...never turned it up past the halfway point. I can't remember the model, but I popped a Yamaha RX-V377 (I know, only 5.1 capable :P). This system is the best sounding (still low balls compared to some of the stuff here), and has more power than I could ever use.
That's about it. Look forward to learning more about this stuff and spending my hard-earned money.
A quick pic of the Living room (has been re-arranged a hair since...( OCD is killing me on the non-matched subs :X )