Intel's been working on mobile processors for phones. They've had a few design wins for their single-core 2GHz Atom. No phones you can buy in the USA though. Reviews for released phones like the Motorola Mobility RAZRi are decent, but didn't seem to knock anyone's socks off. If they develop good LTE integration (they bought part of Infineon a few years ago) and if their management stays committed to this, they may have a chance. Intel was previously a big backer of WiMAX.

Marvell, who bought the PXA line from Intel doesn't have chips competitive with the current generation from TI, Freescale, etc. I don't think Broadcom has anything competitive either, but they don't have much publicly available information.

You've also got Freescale. I don't know if their latest generation (the i.MX6 series) is currently shipping, or how good the OS support is. I haven't heard of any major design wins for them recently, if anyone knows, please post it. If you are focused on the automotive market, this might be a good choice because they typically have CAN bus support.

Then you've got Samsung of course, though you'll be competing against their own products. Apple doesn't sell their chips. That's about it for the majors.

You've got other mid-range chips from low-cost vendors like Allwinner, but I haven't heard of anything from those guys which will allow you to make a leading-edge phone or tablet.

Late addition: According to their website, MediaTek also has a mobile app processor, but it is ARM11 based.