I'm creating a first person boxing game in Opengl as a school project and I want textures and models to apply to it. A look like Wii Sport's Boxing is what I'm aiming for.
Something like this (but, you know, free)
The problem with free is, as the saying goes, you often get what you paid for :)
A good place to find 3D models (from the good to the unbelievably ugly) is the Google 3D Warehouse. It's a huge collection of free models that can be loaded with Google's Sketchup program plus be loaded in to Google Earth if geo-referenced.
From the site, here is a model of a boxing ring that can be downloaded in Collada format as well as for Google Sketchup. You ought to be able to find a way to convert Collada to OBJ.
I like to to use TurboSquid for my models. They've got a lot of variety of free models, in a lot of different formats (md2 and obj included). The free ones are probably not the best ones to look at, but until you find yourself an artist, they're pretty good :)