As long as you have USB ports you should never worry about whether you'll be able to connect your computer to the internet because there are so many types of modems that are made these days that will let you connect. It just depends on your situation do decide which USB modem fits you the best.

What's USB?

USB also stands for Universal Serial Bus. It's simply that small rectangular port on most laptops and desktops with a little plastic tongue inside. It is called Universal Serial Bus because, well, it's so universal (it's on practically every computer made in this century), it uses the Serial protocol for file transfer, and is most definitely a communications bus.

What's a Modem?

A modem is simply a device that allows you to use an analog communications system (like telephone wires) with a digitally thinking machine like your computer. These days modems can convert so many types of communications methods with so many types of ports. In this case, we will be examining all of the different modems you can connect to the USB port on a computer.

USB 56K Modem

There are 56K modems that allow you to connect any computer with USB ports to a normal telephone line. This is a lot like the old days when you relied on a dial-up modem to connect to the internet. Just like in the old days, this modem when connected to your phone lines will tie the line up, so you might miss a few calls, but you're probably exclusively using your cell phone these days right? This modem also allows you to send faxes with your computer and even lets you Skype (voice over IP) for pennies!

USB GSM/GPRS/EDGE Modems

USB GSM and GPRS modems are one of the first steps towards complete wireless communications for computers. GPRS is "2G" data signal that still allows you to transfer significant amounts of data (EDGE being a GPRS signal). Many people prefer 2G over 3G because of how inexpensive it is comparatively while still performing the task they require. These USB modems require you to insert the SIM card associated with your cell phone provider's account.

USB HSPA Modems

For faster speeds you can upgrade to HSPA. HSPA (often referred to as HSDPA or HSUPA) is a member of the 3G family of data signals and coverage in the US for this signal has grown quite a bit. You can typically get around 6 megabit download speeds with HSPA, although you will be paying significantly more. For USB HSPA modems, like GSM/GPRS modems, you have to use the SIM card from your cell phone provider with the modem.

Further Awesomeness

So you've got your USB modem and are wondering how you can make your setup even more awesome.  There is a way you can take your USB modem and make it into a 802.11n wifi hotspot that anyone you want can use.  You'll have to use a mobile broadband router, and I recommend the Kyocera KR2.  It is a full function 3G router that you can use practically any USB 3G modem with.