Sounds like you are going into this head first! Don't worry, that's a good way to start. However, it's also a good way to waste a lot of money. And easy to get sidetracked/misinformed...
Don't worry about the positive ground thing. Somebody is unintentionally messing with your mind 
I like to think of Panels, Batteries and Loads (the laptop, the 12v lights, AA chargers) as being matched. It might work for you, might not..
There is a very fortunate form of electricity delivery mechanism from a 12v solar panel (nominal, 36 cell 12v panels actually put out 20v in good sun but the extra voltage is there for a reason). That is solar panels are constant current devices. That makes them excellent for charging batteries. And predictable too!
So, I like to match my panels to my battery set up. And my battery set up to my load.
What I would do in your case is start is have a couple of different setups, build the smallest first and then when you know all there is to know build your "Dream" system.
For example, a simple setup could be as simple as a 15-20w Mono or Multicrystalline panel with 10 D Nicad D cells, a "ghurd" (tm) dump load controller and a Maha 401fs AA battery charger and a 11w Solsum (Steca) CFL. A 15w panel puts out 0.8A in good sun. It will take at least 12 hours (around 3 days of sunny weather in Summer) to fully charge the Nicad cells from flat if they are around 6000-7000mAh. The Nicads will run a single Solsum (Steca) 11w 12v compact fluoro for 8 hours.
I recommend the above for the following reasons:
"15w" Mono or Multicrystalline panels because they are reliable. A thin film 15w panel will not be as good, be more bulky. Any 15w Mono or Multicrystalline panel IEC rated panel should be fine
"10x" D Nicad cells (quality ones like Sanyo) are better than 1x 12v SLA (Lead Acid) battery because they can be fully discharged and recharged up 1000 times. Lead Acid batteries do not like being discharged more than half and can only handle very few discharges compared with Nicad. You will need a holder for the 10 cells, either make out of plumbing tubing or buy.
Maha 401fs, because it's reliable and runs on 12v (up to 15v from memory). Not particularly efficient. But reliable and fast. 4x AA cells equal 1A of discharge from the Nicads. I like my Maha charger, it's run reliably for a 2 or 3 years now.
A Steca, Solsum 11w 12v compact fluoro. I got mine from the multinational called ghurd.info . It's the best compact fluoro you can buy. I like Warm White, but your mileage might vary. Not cheap
On the topic of AA cells, Sanyo Eneloop are the best money can buy IMHO . They are Low Self Discharge and unlike other NiMh technology, can be recharged up to 1000 times (versus 500 times for normal NiMh)
The ghurd controller because it's excellent (not just for the price), simple and bulletproof.
The above system will be not cheap (for the size) but will last you for some time as everything is very good quality. You might (or might not) need some help putting the controller together (soldering). Ghurd will know of someone who does that. He probably can put all of the above together if you decide to do something like that
The only thing it won't do is run a Laptop for any decent amount of time. That requires a much larger system.
The reason I said "match the panel to the battery and the battery to the load" is that you want a panel that charges you battery fast but not too fast. 10 hours to fully charged is a good amount of time as your batteries' longevity will be increased. You want a load that doesn't put too much strain on your battery. Either setup, ie AA charger or Light bulb will run for a decent amount of time, from memory the AA charger with 4 cells charging takes just under one Amp. That means it will run for 6 hours with nothing going in to your battery. With a 20w panel connected it should run for as long as there is sun (same amount of energy going in to the battery as going out). Same with the fluoro (I measured 0.77A). However, you never want to run the fluoro when there is sun 
One important thing, is you will need figure out where to put the fuses. You will need fuses on the batteries and possibly on the Solar panel. Also a switch is useful too. I run my setups ungrounded (means no ground rod) with dual fuses on both positive and negative return wires. Fuses should be as near the battery as possible. For connectors I've experimented with most types and now use "Fast On" style 6.3mm spade connectors for everything. Spade fuses are cheap and easy to buy too.
BTW, Ghurd is the chap that posted the above answer to your question.
