Short of signing up for the developer program and paying $19, what are my options for unlocking my phone to allow loading arbitrary applications? The ChevronWP7 program shut down earlier this month, which was the only other option I was aware of (which was actually just using the developer program behind the scenes.)
If you are a small business that is privately owned, produces software, has less than 1 million in revenue a year and you're not an employee of microsoft, you can apply for Bizspark. Bizspark will get you AppHub access.. which ultimately lets you unlock devices.
edit: I went and looked into my Bizspark account today, and the process of getting a token isnt there anymore. However, if you are accepted into the program you'll be assigned a local Bizspark associate. They might be able to get you a token, but this isnt a guaranteed process. Please "unanswer" this post. Thanks!
Here's a great guide to the various options available for unlocking depending on the device manufacturer. The below information is from the guide:
Samsung 1st, 2nd generation: Interop Unlock possible with WindowBreak, version 7740 and below
LG (all generations): Interop Unlock possible with MFG application
HTC 1st generation: Interop Unlock possible, see Jailbreaking:HTC 1st Generation
HTC 2nd generation: No interop, jailbreak, or custom ROMs possible yet
Nokia: No interop/jailbreak yet