The Huawei E172 is a small white USB stick, sold at low cost when contracting a 24 month data/UMTS engagment (usually around 30-40 €/month for unlimited traffic).
To make it work under Ubuntu Hardy Heron (8.04), just use the vmc software (see »http://doc.ubuntu-fr.org/vmc ) but consider using the following device:
serial modem
on /dev/ttyUSB0
speed 460800
Have a nice Internet trip with this nice USB stick :)