If you are trying to get a Huawei E169G modem from 3 to work on your EEE then please have a look at this blog post: http://www.greenhughes.com/content/huawei-e169g-easy-way
I've just been helping a friend get her Asus EEE PC working with 3 mobile broadband, which is a service here in the UK that brings a broadband connection to your computer over the 3G mobile phone network rather than using a wired telephone line. Many mobile operators have started offering such a service and it is a great option for people who live in accomodation that does not have a fixed telehone line installed or available, it is also quicker to get up and running than having to wait for ADSL broadband to be provisioned. The major advantage of this technology is that you can use it wherever there is coverage, you are not restricted to your own home. The downside of it is the limitations on downloads, which are lower than ADSL users so may make it unsuitable for some types of broadband use.
The hardware that is provided with the 3 service is a Huawei E220 USB 3G modem, this device is also offered through many other mobile operators. It is supported without the need to install additional drivers in version 2.6.20 of the Linux kernel onwards (you can find out the kernel version for your Linux machine by typing uname -a into a terminal prompt).
On the EEE is is supported and you can use the Network wizard (Internet -> Network -> Create button) to link up with your mobile network. The wizard is pretty much self explanatory, however there are a couple of things to note that might catch you out. Firstly, you should check that you are in an area with a good strong signal, otherwise you will get lots of errors, of occasions when it will not get through all of the steps to connect properly. You may see the 3 network appear on the list of detected mobile networks, but this doesn't mean that the signal is necessarily strong enough. Try to check the signal with a 3 mobile phone if you can and relocate to a area with a strong signal.
When you get to the hardware detection part of the wizard, you will see two entries for the modem, pick the entry for /dev/ttyUSB0. On the page to select the mobile network, you will notice that the user name and password have been prepopulated, you can accept these defaults.
After completing the wizard you should be good to go so have a go at connecting. If all goes well you should now be able to browse the internet on the move! However if you connect successfully but cannot load any pages, you may have had a problem with downloading some of the settings. The first thing to do is to disconnect and reconnect again. If that doesn't work, you may be able to locate problem manually, in the Network program, click on your connection and click Properties. In the General tab, locate the entry for "Preferred DNS server", if this says 10.11.12.13 then have a look at the discussion on this thread on the EEE User forum for a possible solution. I found this happened when I tried to connect, but went away when I reconnected.
The last issue we found was that sometimes, when trying to connect, we would get a message saying "Operation failed" very quickly. It turns out that sometimes the EEE tries to use the wrong bit of hardware to make the connection. Instead of using the E220, it tried to use the internal modem (which I think is missing anyway?). You can easily fix this by going to the connection in Network, then clicking Properties and on the hardware tab click on the entry for the E220 (/dev/ttyUSB0) then click OK.
This all seems to work well once it is up and running and makes for a convenient way to browse the Internet. You will lose some battery life, but you should be able to turn off your WiFi connection (Fn + F2) to save some power.
*** UPDATE ***
If you are using a Huawei E169G modem instead of the E220, check out Dale Lane's blog. I haven't tried this out for myself as I don't own one of these devices, but it looks like he has got this working with the EEE.
*** UPDATE 2 ***
I've just got an H169G, and have written up how to get it working on the EEE at: http://www.greenhughes.com/content/using-huawei-e169g-usb-mobile-interne...
*** UPDATE 3 ***
I've made a package to get the E169G working on the EEE, have a look at: http://www.greenhughes.com/content/huawei-e169g-easy-way