There's not really, or at least, there's nothing much you should try with the graphics card you have. Your best bet is just to use low resolution textures.
I'm gonna have to go with Thomas - I can't think of anything you could outside of turning your video settings down. Overclocking sure, but that's not gonna do you alot of good.
just to clarify a bit. The other options that could improve load times would likely result in lower game performance (e.g. disabling lightmap compression), I assume you'd prefer frame rate over loading time anyway.