Since yesterday (November 8th, 2012) a new bicycle sharing system – Djurgårdscykeln – operated by JCDecaux & Kungliga Djurgårdsförvaltningen is running on Djurgården and is open 24/7 all year round.
The 50 available bikes are not part of the existing SVD Stockholm City Bikes network but can be used (for free) if you already got a City Bikes card or an active public transport (SL) access card. If you are like me and have neither of those cards you can opt for the 3 day access costing as little as 10 SEK.
There is currently one docking station located by Cirkus close to the main entrance to Skansen, the famous open air museum. You can rent a bike for 3 hours at a time and up to 8 times within 24 hours.
Link to Djurgårdscykeln: http://djurgardscykeln.se/en/