Do most European Hotels provided guests with Hair dryers in the room?
Yes I would ask them, but every hotel I've stayed at in Florence, Venice, Paris, London had a hairdryer either in the room, or you could get one from the front desk for minimal extra charge. I would definitely try to find out ahead of time -- but it's likely you will have one.
Can you rent or borrow them from hostels as well?
Hm, in most German hotels, even small ones, if there is no hair dryer in the room alrady you can ask for one and they'll bring it... You might as well request it upon check-in...
Dawn,
Best to call/email the hotel and ask them.
Anna, I would not count on hostels providing hair dryers. I did not see a hair in any of the hostel where we stayed.
When i was in Italy last year there were hairdryersin my hotels, but they were all the kind that hardly blow anything. I was really glad I had manged to squeeze in my travel hairdryer!