Because of these higher charges, not everyone online is checking their email everyday, and response times may be much slower than what you're used to. For most within-Greece purposes, a phone call or fax is still a surer, faster way of getting in touch with a business or hotel than email.
iPass Inc. is another company offering remote access and internet roaming.
Forthnet Internet Services
Established Greece-based company offering Internet access and services. Here's their Services List. Over 65 points in Greece, large local-call cost coverage. Also offers Telecom services. And, you can buy pre-paid Internet access cards
GRNET
Provides IRC software, channels, and connectivity information. Some info only in Greek.
OTEnet
Established Greece-based multi-service provider. Presently the monopoly-holder on Greek Internet access; virtually all ISPs go through OTE lines.
The List - Greek Internet Providers
List, with basic info, on some ISPs serving Greece.

