We can't really suggest specific processors or processor families without knowing your goal.

I have done a lot of work with the Freescale MPC8xx family. Decent processors that may run Linux etc but not so easy to start working with. Not so many reference designs, and not so much working software for these reference designs.

I definitely recommends an ARM7 or ARM9 processor if you want to start with a 32-bit non-x86 processor.

In the ARM world, you have such a huge number of suppliers, and several (NXP for example) have very nice documentation. Freescale may produce thick documents, but they are not always so easy to read. I have several times looked at important sentences and wondered about ambiguities. You do not want to sit with a 2000 page document and wonder which of several possible meanings that is true. And then flip to the next page just to find one more ambiguous sentence.

Another thing is that Freescale have had a tendancy to do things themselves instead of buy existing technology. At least the MPC8xx chps have some form of in-house USB host controller leaving much of the critical stuff to software. Not so fun when they don't develop working reference drivers and the implemented hardware is basically broken and requiring extreme work-arounds... With a reference design bought in VHDL, it would have been enough to adjust initializations and addresses to get existing drivers to work, and work well.