Valtteri flea market (also known as Valtsu)
Every saturday and sunday
Aleksis Kiven katu 17
How to get?
Tram 3B/T and 9 (nine gets you the closest)
Hietaniemi flea market (also known as Hietsun kirppis)
During the summer very popular!
Weekends from 8am-15pm
How to get?
Tram 6, or by foot just walk along Bulevardi.
2nd hand shops:
Fida is good, because it's cheap and you can find very good stuff from there. They also have -50% days, when everything is just stupid cheap!
1. Sörnäinen kurvi, Hämeentie 31. Downstairs there's a supermarket and Fida is just above it, in 2nd floor.
(you'll get there best by metro, hop off at Sörnäinen)
2. Hakaniemi, Hämeentie 5.
(Best you get here with metro. Hop off at Hakaniemi)
3. Central Helsinki/Isoroba, Iso Roobertinkatu 24.
(You'll get here by foot or trams 3B/T and 9)
Here you find also stuff cheap as! Forget capitalism, choose recycle centre!
1. Hietalahti, Lönnrotinkatu 45
(very close to the Hietaniemi flea market)
2. Kalasatama, Hermannin rantatie 2
(more furniture and electronics)
Also there are a few more in Helsinki, check out more info HERE
Also there are Swedish 2nd hand shops, UFF. Anyway these shops are expensive and there has been a little bit of negative atmosphere about their morality around, so I don't recommend you to visit them.
There are smaller flea markets especially in Kallio, I will make bigger issue of them later on...2