Took the car out for its first >20 mile drive in about 10 years today in the form of a commute to work. Noticed that every time the rear axle went over a bump/hole it made a deep series of clunks. Sounded kind of like someone was shaking a few batteries in a 2 liter soda bottle. Didn't matter which rear wheel hit the bump, but it was definitely from the back. Smoothed out quite a bit at highway speeds, though i didn't hit a ton of bumps on the highway either. I'm 90% sure it wasn't doing this before replacing the shocks. Any guesses what's causing it?

Here's the back story:
Car's been sitting in the garage for about 10 years. It's maybe been driven 10 times in this period.
Had to replace all four brake calipers this summer.
Took it to Big O for four new tires. The guy there told me I needed new shocks, struts, and front wheel bearings.
I usually take their recommendations with a grain of salt, but the shocks were old (~16 years is a good guess), and a crap brand, so they couldn't hurt to replace.
I'm starting to believe the strut recommendation, too, since there was a fair amount of "flutter" in the car this morning, making me think the front wheels are doing the failed-strut-vibrating thing.
Replaced the shocks myself. Had to struggle a bit to get the bolt holes lined up, but they went in. One of the biggest struggles was getting the sway bar hole to line up on the passenger side.

Also replaced the stereo yesterday and that didn't have power this morning. And had a headlight out. I don't need any help on those; I mostly just wanted to whine about it.