Most commonly used is 3D Studio Max and Maya. With Max there is an endless sea of tutorials on the internet, especially beginner minded.
Owning any of them can be quite a costly affair. Even with a student licence.
Free options are gmax wich is essentially a watered down version of Max. A cool thing about it is that the exporting tools used for bf2 work in it.
Another free option is blender. I havent tried it personally, but I see and hear good stuff.
I personally like Max best as there is lots of support and I personally find it more intuitive than Maya for instance.
However if you consider Max, Maya, XSI or some program that you have to pay for I strongly suggest you downloading a 30 day trial first. I've seen quite a few people be all like "I want to start modeling!!" and then after only a few trys call it quit.
My best advice is to persevere through the frusting beginner period and just have fun with it instead of trying to achieve perfect realism on your first few models. Play, explore, experiment
