Wireless Internet In Your Car
Here is what I use:
  • Hardware:
    Samsung SPH-a800
    (aka: MM-a800)    		 USB Data/Charger Cable
    (bought on eBay from dwoodsz)    		 Panavise Phone Mount

    Dremel out the RED area.

    Use this magnet and iron plate
     in your phone case.

    PERFECT HOLDER!
    153Kbps total
    144Kbps data max
    estimated 70Kbps average    		 NOTE: Be sure to look specifically for a "Data/Charger" combo.
    The cheaper ones do not charge your phone; you will want to keep your phone charged.
  • Sprint PCS Vision Plan
    "Tethering" your Vision plan to your computer is specifically mentioned when you select your vision plan:
    "[Sprint PCS Vision] plans are not available with PCS Connection CardsTM, PCS Connection KitsTM or other devices that can be used as a modem."
    Furthermore, it is similarly mentioned in the service agreement.
    "Sprint may deny or terminate service without notice where use is in connection with server devices or host computer applications, other systems that drive continuous heavy traffic or data sessions, or as substitutes for private lines or frame relay connections. PCS Vision Packs are: (a) only available with a Vision capable PCS Phone or PCS smart phone device; and (b) not available with Connection Cards, Aircards, or any other device used in connection with a computer or PDA - including phones, smart phones or other devices used with connection kits or similar phone-to-computer/PDA accessories."
    However, people have been "tethering" with few complaints from Sprint for awhile now.
    As long as you don't "drive continuous heavy traffic or data sessions" you should be able to get away with it.
    Search this site for "tethering", "777", or anything else you think makes sense: http://www.sprintusers.com/forum/
  • Samsung USB Driver (perhaps not necessary)
  • Go to the Sprint PCS Software Download page and get the "(Vision/PCS WiFi) PCS Connection Manager Software for Airprime PC3200/USB Cables"
Here are a few other wireless internet providers:
  • T-Mobile
  • Cingular
  • more...

I do NOT care to get in to a religious discussion about which provider is the better.
I chose Sprint, and I will stick with it until I am unhappy with it.
 

In addition to cellular internet, you can also use a WiFi 802.11b or 802.11g USB adapter.
These are easily discoverable on the web, so I will let you do your own research.
Old Hardware:
Sanyo 8100 Phone USB Data/Charger Cable for Sanyo 4900/5300/8100 Panavise Phone Mount

Dremel out the RED area.

Use this magnet and iron plate
 in your phone case.

PERFECT HOLDER!
153Kbps total
144Kbps data max
estimated 70Kbps average		 NOTE: Be sure to look specifically for a "Data/Charger" combo.
The cheaper ones do not charge your phone; you will want to keep your phone charged.
NOTE: The Sanyo SCP-5300 seems to be a better phone