This one has loads more of a tourist board site. Some accommodation may have phone numbers only but you may find web sites for some of them:

http://www.gto.gr/

This one has some nice hotels and you can pay by credit card- I've used them and know the company is good:

http://www.yourgreece.gr

- or just google the word accommodation followed by where you want to stay, it will take a bit of trawling but there are lots of tourist sites with links to local accommodation

I know this is a bit late, but it might help someone for next year. We have found the Olympic holidays website very good for accommodation only in Greece and Cyprus. We booked with them this year and only had to pay a deposit and the balance 8 weeks before. Can get some cheap last minute flights on there as well. Make sure you check out the reviews on HT before you book!