Google Voice comes to mind: it's free, provides a separate number, and is (seemingly) independent of the primary carrier. There are definitely a few caveats though. Upon looking closer, I discovered that using GV on a phone, even an Android phone, is not VoIP; GV merely provides an intermediary number as a rendezvous for calls. In this scenario, GV is still using the primary carrier. This fails to fulfill points 2) 3) 4) and 6). Further, GV spoofs caller ID of incoming calls so that they appear correctly. This seems to obliterate point 5). Though GV doesn't support calls over data, it was brought to my attention that upcoming versions of Android will have native support for SIP, the underlying VoIP protocol used in desktop versions of GV. Would it be possible to use GV on Android over data in order to solve these problems, such as the Gmail GV interface with Flash (which would be inconvenient as all)? Another tiny point of consideration is that GV integrates with the phone's main contact list; I would prefer them to be separate, such as in Skype. In the future, GV may provide everything I need, but for now, GV for Android doesn't meet my requirements. (And if someone could confirm all of this, that would be great.)
This brings us to Skype. Probably the world's leading VoIP provider; it's inexpensive, works on Android, allows you to call phones, gives you a number, and is VoIP, and therefore independent of the primary carrier. Skype, however, is not perfect either. The main thing that draws my attention is Skype Mobile. Skype Mobile is not Skype on Android (that app is just called Skype), but rather it appears to be an app released by Verizon Wireless. a) I do not want any of Verizon proprietary software on my phone, b) it is made clear that these calls are carried by Verizon and charged to your bill. I need clarification here. It is my understanding that a Skype call would be carried by Verizon from the app over the voice channel, to Skype, and then to the recipient's phone. (Skype to Skype calls are still free.) In this configuration, Skype seems to operate in much the same way as GV, and might present the same shortfalls concerning points 2) 3) 4) 5) and 6). Because I don't know even know this for sure, much less the details of how it works, I can't say which points it would infringe upon specifically, but I would rather not take any chances. (Clarification here would be much appreciated.)
Here's the huge question though, can the regular Skype app for Android be used with the Motorola Droid on Verizon? It's an important question, because if the answer is yes, that would fulfill all of my requirements listed above. That is to say, using the Skype app for Android (not Skype Mobile) calls would be carried over data (3G or WiFi hopefully, I thought I read it was one or the other), independent of the primary carrier, freeing me from constraints, and protecting my privacy. It seems like there would be no reason for Skype Mobile to exist if it were possible to use the regular app, but I don't know. True VoIP would still have some limitations though, such as the large amount of data usage. Though I have unlimited data, if I use too much, they might complain, also 3G or public WiFi might not be fast enough to support Skype calls. Also, a huge lingering problem would be texting over Skype. Whether or not you pay by month or by minute, texts are always charged individually. I would miss the unlimited texting I get from Verizon, not to mention Skype texts are a bit pricey at $0.112. Being that texting is probably my primary means of communication compared to calling, that could be a bit of a hindrance. I'd rather not have to pay ~$40/month for texting alone, in addition to my Verizon plan. (Technically I could use GV for texting and Skype for calling, but again it would be hugely inconvenient.)
As you can see, there's a lot to consider, and it can be kind of difficult when you get right down to it. Of course, GV is free, so trying it can't hurt, even though at this point it doesn't seem to do much good for me. By no means are my options limited to Skype and GV, if you have any other suggestions I would love to hear them. If you have any clarifications, thoughts, ideas, or just your opinion, by all means post a reply. In the end we all just want a little freedom

Thanks,
Zach