First I'll go into some personal history. I'm currently an AT&T and Verizon wireless customer. I've been an AT&T customer for about 4 months, previous to which I'd been on T-Mobile for about 4 years. I've been a Verizon customer for about a year now. I have the iPhone and also an LG enV.
Ok, so first off, Blackberry's aren't of much use to the typical young adult. It's more suited for business types and whatnot, plus with the added internet/data package you have to get for them, it can get pricy.
I've got the iPhone and well, for what it's worth, it's a decent phone. But it's far too much trouble to deal with the service and whatnot. AT&T's been nothing but trouble for me ever since I switched over in November. The minutes are different, they've charged me for unused data, and the texting packages are just so much trouble too. All in all, I've been very unhappy with it. Having said that, AT&T does have some nice phones if you're into that.
All the major providers aren't limited to regions, if I'm understanding your question. Your choices are probably gonna be AT&T, T-Mobile, Sprint and Verizon. Skype phones, as far as I know, do not exist.
SMS (short message service) is just another term for text messages. While MMS are multimedia messages, like picture or video messages.
Unlocked phones are basically phones that are not tied down to any one carrier. Most phones are locked to their specific carrier, like the iPhone being locked to AT&T. But most, if not all, unlocked phones are GSM phones, meaning they work with carriers that use SIM cards. AT&T and T-Mobile have GSM phones, so that all your data and whatnot will be stored on that small card. Verizon and Sprint are CDMA, so the information is tied to your phone rather than a card, I think.
Mobile to Mobile basically means that, if your plan supports it, any call to someone on the same carrier (Verizon to Verizon, AT&T to AT&T) is free.
It doesn't cost money to take pictures, it may cost money to send the pictures through text message if you don't have a text plan that covers.
And many phones do record video, some better than others.
So now that we have all that through with, let's get onto the phones and service. Of all the services, T-Mobile's service is the most affordable. They have decent coverage and work as advertised. AT&T is a little pricier, but not much. It's supposed to have better coverage, but after having been a T-mobile customer for 4 years and now AT&T for 4 months, I've found very little difference between the two, apart from the terrible billing problems. So, the extra I'm paying for AT&T is definitely not worth it, and in retrospect, I'd go to T-Mobile.
Sprint- I don't know too much about. My friend uses Sprint and she's happy enough with it. I've always thought it was more business oriented than anything, as you could tell by most of their phones.
Verizon is another service I'm using and it's been great. It's a bit more expensive, too, but I haven't had any problems with it at all. For that little extra, I think it's totally worth it.
The only thing is that Verizon is much more of a closed provider than say, AT&T and T-Mobile. What I mean is that, you're basically tied to whatever phone Verizon offers you. You can't change your mind on the phone and then go off and buy an unlocked phone and switch sim cards. Verizon locks down bluetooth transfers and if you want ringtones and whatnot, you have to buy them from Verizon itself.
With an unlocked phone, you can basically make your own ringtones, and just fiddle around and do more things with it. Though buying unlocked phones is costly, as well.
Anyway, I'm going round about, I think. So, I'll stop it at that and see if anything I said makes sense to you. Also, if you have any more questions, do ask away in here. I'm sure you'll find an answer.
Now onto phones. I'm gonna assume you're going with either T-mobile, AT&T or Verizon, so I'll focus on those phones. I'll stay away from Blackberries, and smartphones (i.e., phones using a Windows mobile OS) since I think they're unduly complicated for a first phone and you seem to be more into multimedia than anytihng else. So I'll suggest some multimedia phones for you.
AT&T
http://www.wireless.att.com/cell-ph...details/?device=LG+Shine(TM)&q_sku=sku1130019
http://www.wireless.att.com/cell-ph...0i+Walkman®+-+Black+(Refurb)&q_sku=sku1190009
http://www.wireless.att.com/cell-ph...ice=SYNC+by+Samsung+(Refurb)&q_sku=sku1150003
T-Mobile
http://www.t-mobile.com/shop/phones/Detail.aspx?device=11e9c7d4-94d1-4d79-bc4b-ec2cc238a4a9
Keep in mind that with a Sidekick, T-mobile requires you get a $20 data plan for the messaging and whatnot.
http://www.t-mobile.com/shop/phones/Detail.aspx?device=f34e6f5f-52a0-43cc-ac13-8e7329dc5da3
http://www.t-mobile.com/shop/phones/Detail.aspx?device=04de47b4-1bc4-4b9b-b644-0a058792e71c
The RAZR2 is also offered by AT&T and Verizon, just so you know.
Verizon
http://www.verizonwireless.com/b2c/...l&selectedPhoneId=3218&changingCompletedOrder=
http://www.verizonwireless.com/b2c/...l&selectedPhoneId=3098&changingCompletedOrder=
http://www.verizonwireless.com/b2c/...l&selectedPhoneId=3406&changingCompletedOrder=
http://www.verizonwireless.com/b2c/...l&selectedPhoneId=3299&changingCompletedOrder=
Ok, so these are most of the phones I think you may like. But I don't know your preferences, so you may hate them too. In any case, you should always go to your local stores and check out the phones too, if any of them catch your eye. It's always nice to get a good feel for them and know what you want from them. So, hopefully this helps.