[Galaxy Note GT-N7000 General] Hirudin:
Disclaimer at the bottom of the post... *

Updated for ICS / Ice Cream Sandwich - tentative settings, please confirm if these work for you. (Look for additional red text.)

Thank you to everyone who took the time to figure all this stuff out! All I did was take some pretty screenshots to make it easier for beginners.

OK, I want to make this short, simple, and thorough. I don't think those things are mutually exclusive. :)

First, you need an activated Straight Talk SIM card that can be transferred to other phones. **

Put the SIM into your Note, turn it on, and open the system settings. Then tap the following...

Wireless and network > Mobile networks > Access Point Names

The next screen should look something like the attached image #1: "APNs". Tap the Menu button and tap the New APN button. ***

You need to create two APNs. The name you enter in the Name field apparently doesn't matter. I just used "Internet" and "MMS" to avoid confusion. Copy the settings in the two attached image numbers 2: "APN_1" and image number 3: "APN_2". I drew a yellow check mark next to all the entries that I needed to change, I suppose some firmware versions/ROMs/phones may be different. When you're done entering in all the required addresses and stuff, tap the Menu button and tap the Save button.

APN 1...

Name: Internet

APN: att.mvno

The method for setting the "APN type" varies. Choose "internet" if you are given a list of choices, type "default" if you must type it in.

APN type: internet

APN type: default

Typing "default" seems to work on imilka's AOSP ICS v03 ROM for the internet at least, I haven't tried MMS yet. I suspect it will work with other ICS builds as well.

APN 2...

Name: MMS

APN: att.mvno

MMSC: http://mmsc.cingular.com

MMS proxy: proxy.mvno.tracfone.com

MMS port: 80

APN type: mms

When you save the second APN and you return to the APNs screen: select the radio button on the first APN (see attached image number 4: "Select_APN").

Tap the Back button to return to the Manage network settings screen. Put a check mark into the Use packet data option (see attached image number 5: "Check_use_packet_data"). Shortly after checking that box my phone connected to the network.

Yay you're done! This worked on my phone, I hope it works for y'all too.

* This is for informational purposes only. I am not an expert. Frankly, I don't even know what these settings really do. I simply copied them from other places on the internet (like this thread). There is an app, APN Backup & Restore, that can be used to (gasp!) backup and restore your APN settings, if you're nervous about doing this I suggest you backup your current APN settings before proceeding. It looks like there are other APN settings apps, it's possible one of them is better... I dunno. Personally, I did not use any APN-centric app, though I did have a backup of my whole phone made by Clockwork Mod ROM Manager

** I am no expert, but people on the internet say the only way to get a transferable SIM is to buy a Nokia E71 or a Nokia 6790 from Straight Talk. Check out straighttalk.com, they might be selling a refurbished E71 or 6790 (currently the refurbished 6790 is ~$50 with free overnight shipping). Personally, I left the SIM in my Nokia until the service was activated. I saw someone on the net say that you should switch the SIM back to the Straight Talk phone before calling tech support. I don't know if this is really something you have to do or not. Personally, I'm going to keep the phone around and use it whenever I have to call them.

*** If your screen shows some APNs already I'm afraid I don't know what you should do. I suggest you stop using my guide and see if you can get some expert advice elsewhere. I'm sorry about that!