Q: I need to use my USA prepaid in Canada. What are my options?

A: Not a great selection. One of your best choices may be to buy a local SIM when you arrive in Canada

PagePlus Cellular PAYG
Voice: 60c/minute
Text: Same rate as US (no surcharge)
Data: Not available

Boost Mobile iDEN
Voice: Not available
Text: Same rate as US (10c/text or plan package - no surcharge)
Data: Same rate as US

T-Mobile PAYG
Voice: 69c/minute
Text: 10c send, 5c receive (same rate as US - no surcharge)
Data: $15.00/MB

eKit
Voice: 29c/minute (plus 50c per call fee)
Text: 25c send, 10c receive
Data: $15.00/MB

TruPhone
Voice: $1.05/minute to make a call; 70c/minute to receive a call
Text: 56c send, free receive
Data: $2.78/MB
  (tax/fees not included in rates above, add about 10%)

Q: I only want to text. I don't plan to use much voice if at all. It seems like a waste to get a regular plan and pay $60.  Even if I get an add-on plan it's likely at least $10 plus another $20 for text. What is the best deal for me?

A: There are now several options. I put them in my perceived value order from best to worse, but of course your mileage may vary.

#1 - T-Mobile To Go Prepaid. $15.00/unlimited text and 10c/minute voice. Limited roaming ability (typically can not use the AT&T network).

#2 - AT&T GoPhone Pay As You Go Prepaid.   $5/200, $10/1000, $20/unlimited. Good for 30 days. It's a pretty good deal for included SMS and MMS. No extra data charges. Currently international text is included in the packages. Texts will carry forward as long as you refill before the 30 day expiration. Downside is that PAYG does not roam on many networks so check the map! Also you have to call AT&T and renew over the phone which is annoying. AT&T finally disabled the annoying service alert after every text if there is no balance deducted (e.g. using text package).

#3 - PagePlus Cellular Prepaid. $11/2000, $20/5000 (likely will be switched to unlimited in August 2009). Good for 30 days. Uses Verizon network. MMS data costs $1.20MB. No extra cost to text when roaming. Downside: MMS costs extra. Texts do NOT carry over month to month.

#4 - Virgin Mobile Prepaid. $5/200, $10/1000, $20/unlimited. Good for 30 days. Downside is no service outside the Sprint PCS network (no roaming capability). Texts do NOT carry over month to month.

#5 - Verizon Wireless Prepaid.  $10/250+Unlimited M2M text, $20/unlimited. No extra cost to text when roaming.  Texts do NOT carry over month to month.

Q: I only want to use data.  Not a lot of options. Data is the future of wireless and the providers are not going to give away the farm.

#1 - AT&T GoPhone Pay As You Go Prepaid.  $5/1MB, $20/100MB.  If you are not a data hog and do not stream or look at large HTML pages then this might work for you.  Your balance will carry over if you refill before the expiration date but I understand you are limited to a 300MB account limit at one time.  Best deal would be to get the $20 100MB package and then renew with the $5 package (assuming you do not use all of the data each month). If you have a device with WiFi this option is not bad. AT&T has been attempting to keep iPhones off of this plan so be warned if you are trying to use that.

#2 - T-Mobile To Go Prepaid. No data plan, but you can switch to the Sidekick plan for $1/day which includes unlimited SMS and data. Voice is 15c. Downside: You need to set up your phone for data unless you actually have a Sidekick. Also, you can switch only for the days you want to use it, but it's not a good deal if you want to use it every day (and you have to remember to switch plans when you don't want to use it). Limited roaming ability (typically can not use the AT&T network). Looks like this loophole is closed.

(more options coming as I get around to it)

Q: Can I bring my phone with me to a new cellular provider?
A: Probably not. The most important thing to remember is that the different technologies are incompatible with each other.  A phone that works with one technology will not work on another.  Even when a phone may be compatible between two different cell companies, many times the phone is "locked" so it can't be used anywhere else.   Even if you get past the lock, you probably can't use data because it is hard coded to a specific carrier.  With GSM it used to be that you could simply switch SIMs but now there are so many differences, especially with 3G, that you have to be careful. You might have to "debrand" and will likely have to "unlock" the GSM phone.

Q: What are the different cellular technologies?
A:         (click the acronym for details, thanks to about.com)
    CDMA (Verizon, Sprint PCS, U.S. Cellular) 
    GSM  (AT&T, T-Mobile)
    iDEN (Sprint Nextel)
            (the following technologies are now obsolete in the USA):
    TDMA
    AMPS

About.com Cellular FAQ

Questions to be answered as I get time:

Brief History of Cellular in the US?

What about Cellular in the rest of the world?

How do I get started?

Why do you want a cell phone?

How do I choose a cellular service provider?

How do I choose a cell phone?

What's all this I hear about contracts and early termination fees?

Why does it cost so much to upgrade my phone?  I got one free when I signed up.

What are your expectations for cellular service, and then we'll tell you how it really is!

Why can't I use the same cell phone when going from one cell service to another?

Can I use my cell phone in Canada?