Some of you may find this interesting, some may find it crazy, mostly you'd find it to be lots of clicking. Planetary Interaction is the farmville of EVE, but it can net you a nice profit at the same time (especially if you are already multiboxing anyway) as you're doing other things like mining/missioning/plotting to take over the universe. My current project:

I have one main toon on each account, so I've turned the other two "empty" toon spots into PI toons. I didn't total up the time, but a brand new toon with zero implants can be level 3 PI, level 3 industrial ship (of whatever race), and level 2 hull upgrades for expanded cargohold II's in 5ish days. ISK costs are about 25mil per toon for skills, ship, command centers, and setup for 4 planets.

I would suggest not trying this until you have at least something that can haul a good amount of m3 (think Orca, or bigger). It takes me multiple trips just to pick up all of my P1 materials, so a regular industrial ain't gonna cut it for moving a 35 planet strip mining operation's worth of materials to a hub.

For planets, I stick with ice and gas (and experimenting with lava) because they tend to have good prices for the P1 oxygen and water and a LOT more resources on each planet than if you chase some of the smaller stuff (a lot of which has a bad money/time ratio anyway). I'm not currently doing any P2 or above for the simple fact that I haven't messed with it yet and it adds a layer of complexity to an already big clickfest.

I'm also setup close to a nice hub for selling stuff (think Jita, Rens, Hek, etc). The fewer jumps you have to do with your materials the quicker you can sell and go do something else. Remember, we want the least work for the most profit with this. I know lower sec systems get your a higher yield, so feel free to setup in the closest thing to low-sec you can find near a hub. I personally don't worry about this as much right now as it would tack on a lot of jumps to my hub and back home.

So what am I actually doing? Get some good PI setups out there and start soaking up planetary resources. Set your extractors to run for 2 days, 1 hour, 30 minutes to keep the cycle time at 30 minutes. Try and hit two different pockets of resources at once reasonably spread out but running back to the same starbase. (Check out the PI tutorials on youtube if you havent done any PI). Pick up your stuff every four to six days. Let it stack up in your home station until you get a boatload. Run it to the hub (even if one thing sells better in another place, save time by bringing it all to a hub if you can). Sell, rinse, repeat. You can reset the extractors without even undocking your ship (and if your resources are still good in the location you are already set up at it's as simple as stopping and starting the extractor program and then going to the next planet).

Ok, anyone who has done PI is saying yes yes, all of this is obvious. Ah, but what's my goal? I run 3 accounts and right now I'm out to make at least 2 of the 3 self sustaining with plex entirely from PI. I mission and play around with other stuff, but I'm really looking to try and make the most of the three characters on each account that I never ever have used in the past. Maybe it's something you want to try, maybe not. We'll see how the experiment goes.