3DsMax - Good all round program
SketchUp - Easy to pickup, but is useless for overly complicated tasks (especially organics), has some issues when exporting to max.
Lightwave - Never used it, but if Lurri and Ry use it...
XSI - XSI users are like fireFox users if you don't use it they will hound you to death to download it . Its is ment to be a high quality professional package.

A few Devs use lightwave. I know Luuri is one of them, and he is one of the fastest modellers I know.

I don't know which would be best for beginners, but out of the programs I use (3DS Max and Lightwave), I would say lightwave is easier to pickup.

You can get a free version from softimages site ....its called XSImodtool (free forever) or you can get 30 day trials of the retail versions.

You should try Lightwave if you're just starting out. It's a very easy program to pickup and learn. It's got a lot of flexibility as well. After a couple weeks of using Lightwave I was confident enough to make what I call a "McTemple".

If you want to make stuff for fun, I heard that Sketchup is ok, if you don't plan on using the model for anything.