My suggestion is go and download a freebie software or Maya learning addition... or one of the other expensive learning additions... Then go to different 3d sites and do tutorials...
Also what do you want to do 3D for? Personal art? Game models? Movies? Advertising? Graphic Design? these things are important..
If you can model in one software you can model in all software it is just a matter of learning the tool set..
A new program called Modo is coming out by Luxology.. It has a lot of promise.. it will be 500-600$ when it first comes out which is a reasonable price.. another inexpensive modeling package is Silo.. its about 100$...
Like someone said XSI is 500$.. Not too shabby.. Also XSI has a lot of support and tutorials out there...
but its up to you..
One program that is out there too is Zbrush.. but don't be fooled into buying it to model.. First learn to use a actual modeling package first.. Zbrush is great for doing hi-res work... but after you have made your models in another package.... so holdoff on that..
anyhow.. good luck
"Live each day like you will die tommorow, and dream like you will live forever..."