As m_sparks mentioned, a free GSM cellphone can be very handy.

http://prepaid-wireless-internet-access.wetpaint.com/ is a nice starting point to look for prepaid deals before starting your trip. Starter kits including SIM card and a certain amount of MB can be bought in phones shops, books shops.

Prepaid/PAYG data SIM cards are pretty cheap now (except in France ( ), and an average deal is about 25$ for 1 GB

And do not forget to install Maemo-Mapper and preload maps of the areas you planed to visit.