Let's put it this way: There's tons of stuff YOU can do for free, but it's at the cost of someone else. You can slap Midnight Madness boards or go to Lucky chairs, but someone had to pay the bucks for the L$ to put that store there, You can sight see (if you don't crash 20 times trying to teleport or spend 30 minutes rezzing cause the place is crowded), and again, someone had to pay the big bucks to have that land to build on, not to meantion they spent L$10 for every texture uploaded for every building, clothing item, skin, etc. That is, unless they BOUGHT items to put on their little spot of land and that would be more than $L10 most of the time. The average price for renting a parcel of virtual turf is around L$1800 a week for like a quarter sim. Just so you know, Premium Members who actually bought land spent $1000 (real money) to get it and pay an additional $215 (again, real money) a month to keep it.
So go out and enjoy what you can, but be aware that everything has a price in Second Life. That "fun and awesome club" you visited and liked dancing at might not be there tomorrow because the owners couldn't afford to shell out the L$ themselves and no one donated to them to keep the place running and no one tipped the DJs so they all quit.
All the haters can scream and flame me all they want, but it's the truth. There are fun and free things to do in Second Life, but they cost someone a pretty penny and unless they get some of those pennies back, the free fun stuff will go bankrupt and close down.