I finally got around to trying Linden Realms. You can make a few Linden dollars there, emphasis on a few. The blue and green crystals are worth the most, but those crystals are few and far between. The next most valuable are the orange ones, but you need fifty of those to get five L$. After that comes yellow and pink.
If you try to fly, the clouds will get you and teleport you home. On the ground are these big fish looking things. If they get you, you get teleported to a starting place in Linden Realms. Anyway, it's a way to kill a few hours and make a few L$. You would be better off doing almost anything else though to earn Linden dollars.