Here are links to a few suggestions on where to stay during the seminar.
Hotel Karlaplan is a nice hotel situated at Karlaplan. There is a limited number of rooms to the discounted price of 999 SEK for a single room and 1199 SEK for a double room. State Tech-Diving 2006 when booking.
Hotel Arcadia is a more affordable hotel situated very close to the seminar. State KTH when booking and you'll get a single room for 595 SEK and a double room for 745 SEK (Regular price 695/795 SEK).
Vanadis Hotel is a rather cheap hotel within walking distance from the seminar.
Rooms start from 499 SEK.
Abbes Budget Hotels
Abbes Budget Hotels is centrally located at the Central Station, Slussen and in the old town. Dormitories 220 SEK, single rooms 450 SEK and twin rooms 595 SEK.
STF Hostel Fridhemsplan
The Swedish tourist association has many hostels in Stockholm, one of the closest is the hostel at Fridhemsplan. Beds start from 195, rooms from 390 SEK.