Following is an uncomplete list of maybe alternatives for the raspberry pi (if it fits to your needs). The common intersection of all listed items is "usb, hdmi out, linux driven".
It should be clear that the raspberry pi has a philosphy that differs from the rest :-).
Ladies and gentlemen, set your alarms!
The Raspberry Pi Foundation will be making a big (and very positive) announcement that just might interest you at 0600h GMT on Wednesday 29 February 2012. Come to www.raspberrypi.org to find out what’s going on.
The good news is that this finally means we have a date for the first batch: the boards will be finished on February 20. Eben and I may be going to China to make sure that the boards can be brought up properly for that date if necessary. We’ll be airfreighting them to the UK immediately, so you should be able to buy them before the end of the month.