I just got information from this year’s Finncon that
some of the hotel quotas will be released at the end of the month. Some rooms will be available until the date announced earlier (June 14), but if you want to make sure you get the room you want, you should book now. More info on the convention web site. Update: the convention staff confirmed that all the rooms will be available until the announced cutoff date after all—their earlier info was premature.
Note: the reservation codes don’t work for Internet booking (at least for every hotel)—you need to e-mail or call the hotel to get a room for the (very good) Finncon rate. Update: The reservations made with the convention code can be cancelled without penalty up to the previous day before the check-in date.
There will also be floor accommodation offered by the convention if you want a very inexpensive place to sleep. The accommodation is at a couple of schools very close to the convention sites (about half a kilometer away); the price is 5 euros/night. There are showers and microwaves at the accommodation, but bring your own sleeping bag and other stuff you need—only floor space is offered at the place. To sign up, fill the form and pay to the Finncon bank account in advance. The floor accommodation will be open on Friday and Saturday nights, from 6 PM to 10 AM next morning.