I'm a thirtysomething map-o-holic who found the OSM at autumn 2009 and found it more than an interesting project.
As a GPS device I use my Nokia C6-01 with Sports Tracker  which does the trick with a good enough quality.
As I live in Helsinki, I've added already lots of details of the near areas based on the Yahoo images and my local knowledge. However there seemed to be an empty spot at the map at Itä-Uusimaa called Porlammi . That's a village where I spent 10 years of my life and I still visit there time after time. So I took a priviledge for mapping it from scratch. There were only two roads GPS'ed so lot of work is to be done...
Porlammi at OSM: 
There are appr. 80km of named roads plus tons of unnamed tracks. My intention is to get a GPS track from all named ones and get at least the main forest tracks that I know. Most likely all the required GPS data is gathered during summer 2010. Also adding as much local knowledge as possible is one goal. All the cliffs (there are plenty), rapids (as well), schools, shops etc.
I already asked (2010-01-27) some GPS data from the Lapinjärvi municipality and waiting at least some answer :)
Status of the Project Porlammi:
70 named roads ~80km in total
87% of them already drawn to the OSM, at least by Yahoo and local knowledge.
59% complete (GPS track, names both in Finnish and Swedish, surface, lights, maxspeed)
Going further and mapping also adjacent villages at Lapinjärvi, Rutumi and Ingermaninkylä, and other near by areas.
I play keys and scream backing vocals at two bands:
Far'n Beyond 
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