Cheap UMTS/HSDPA Router:
Use a USB UMTS/HSDPA surfstick (e.g. Huawei E510, E220), mostly they come with 2 GB SD Card Reader.
Install Lenny due to missing wvdial support at squeeze...
Add as much services you like (IPCop, samba, NFS, WU-Ftp, Apache2, PHP etc...)
Install Webmin with all needed modules...
Maybe add Wifi-USB Card and pop-up you own local UMTS/WIFI Cell... (not tested yet)
Performance is quite O.K. Those who start picking on performance: Yes I know what kind of hardware's ticking inside!!