How long you been away? I was out for a decade... settled right back in.
Lighting: I was all excited about LED's when I got back in. Couple years later, I'm back to T5's, thanks. So far, I've never found anything that surpasses T5's for coral health.
Skimmers: Haven't really changed, just got more efficient... and far more expensive.
Automatic dosing pumps have come a long way...
Controllers were fairly new when I got out. I picked up a Reefkeeper Lite this go round. Works great, dead simple, not much more expensive than a few good timers.
I was in during the DSB craze... all but gone these days.
Controlling nitrates and phosphates used to be a full time job. A decent refugeum and some GFO, and you'll be reading posts about people DOSING nitrate and phosphate.
Number one: Internet vendors!
BRS (great vendor, but check their pricing before you order!) and many more. I'm out in the stix, so this one is a major asset to me.
Enjoy!