Do you think it is safe to overlock my laptop's 8600m GT a little bit without adding extra cooling?

Try it and see what happens :-P

Seriously, overclock it a bit, see what it does to temperature, then take it a little bit further... It should be safe unless you really overdo it.

The fact that we are talking about a laptop doesn't really make it a very good candidate for overclocking due to the cooling limitations. You could try it, but I wouldn't push it too far, you could end up cooking much more than just the video card.

Oh yeah I should probably add that I actually tried on my laptop's graphics card and the temperature spike was big enough to realistically DECREASE the performance. So yeah, it's not something you SHOULD do of all things, but it might work - just be careful. Please.

Not recommended. Notebooks are not meant to be overclocked.

Maybe my 8600m GT isn't being pushed hard enough right now because the people who made my laptop didn't want it to use too much power?

They've had a reason for that. They didn't want the thing to burn down.

Well it will probably make my video card die sooner and there is a huge risk of my laptop being ruined like you guys said so I decided not to.

Best to do a search on google and see if anyone else has tried it on your make and model of laptop. My little netbook is quite happily overclocked by a bit and it could go further if I felt like pushing it but I always remember the weather.
You have to remember that ambient temperature and humidity changes year round and unless you're doing it on the hottest day of the year it's a bit of a risk to push it because it might be fine most the year but all it will take is one exceptionally hot day and you risk irreversible damage. Also bear in mind that it's not easy for heat to escape a laptop and most onboard graphics chips only have a passive coolant device (such as a heatsink). Also if your fans get clogged, further restricting airflow this can kill it very quickly.

I doubt you'll see much of a performance increase anyhow to be honest. You're better off trying something software wise to squeeze a little extra out of it. If you want a performance boost, set the Nvidia control panel settings to Maximum Performance and get used to lowering and disabling things that have minimal graphical effect in your games but can be resource heavy (like high quality shadows.) Or do a few balancing tricks such as lowering the in-game resolution and upping the anti aliasing or vice versa. You'll also find your card does some things better than others.
Finally you can try using Game Booster which I use from time to time on my netbook and I squeeze an extra 3-8fps on average from my games using it. http://www.iobit.com/gamebooster.html

You know you could try all other kinds of tweaks, like disabling aero stuff from windows, defragging fragmented games that run slow, that kind of stuff. Google for tweaking guides. This, gamebooster's often quite amazing

Laptops run hot anyway. If you overclock it you might fry your motherboard. You might see a small increase in speed, but it's not worth it unless your willing to buy a new laptop if you mess up. Don't do it.

Well there's not really that much of a risk if you're careful and do a benchmark after every increase, while possibly decreasing safe temperature in BIOS if you can.

There are many notebooks that get defective because of excessive GPU heat even without overclocking.
Knowing this I would recommend downclocking instead... :P :)

If I downclocked, I wont be able to play games made after the year 2000. :P

I share your pain, man. I actually stripped my windows of all functionality I don't immediately need, browsed trough drivers until I found the one that seemed to work the best, I was even messing around with increasing HDD access speed SOMEHOW since notebooks don't have it too fast. I ended up with machine slightly faster than when I bought it, and it's still not enough. I. Need. More. POWER!