Wind has the Mega options (
see here) which are very good, but unfortunately it has quite a small 3G Network (and even smaller if we talk about HSDPA). No problem if you are going to bigger towns.
You can go with "
3" which has the widest coverage and the "Naviga 3" option is good (9€/month for 50MB every day).
Of course in both cases you need a 3G HSDPA modem working on the 2,1GHz W-CDMA network (both Wind and 3 have them in their shops, from 50€ and up...).