I'm based in London. I work for placr.co.uk on projects relating to transport information and GPS data analysis. Previously I worked for a while at CloudMade as part of a team working on furthering the goals of OpenStreetMap.
Including blog category 'maps' although I'm planning to make more use of...
When I first joined I did a very unfashionable thing of going out mapping without buying a GPS using pen and paper and yahoo aerial imagery. Very low-tech, but it does work and work. Walking Papers (and its spiritual successor, Field Papers) has made these ideas more fashionable, and these days I think it really should be stressed to newcomers that you do not need a GPS to contribute.
I did buy a GPS of course. I have a NaviGPS GT-11, and for years I used this in conjunction with a normal compact digital camera to do Photo Mapping. Working with the photos in JOSM, this is still the most efficient way of surveying of many details. But in fact I've gone back to basics and started ditching the GPS for a lot of my contribution lately. I still use a camera a lot. This is partly because these days I'm doing shorter mapping stints. Quick bit of data capture down one or two streets, or even just a single shop when I spot something that's changed. For serious mapping sessions I need to remember to charge up the old GPS.
My NaviGPS is also waterproof. Useful for WikiProject Whitewater Maps! I don't have a car, so aside from kayak mapping, I'm generally on foot... although I have also tried roller-mapping!
When I first started mapping I championed an "armchair mapping" approach involving sketching in road layouts over the Yahoo! Aerial Imagery in some areas where I am not necessarily planning to complete the mapping myself. I thought a two-phase mapping approach would work well, as an efficient way of combining rapid aerial imagery sketching and on-the-ground hard work. I realise now that armchair mapping can have a negative community-quashing effect. It's somewhere on a sliding-scale of evil towards Imports. Blatting areas of coverage rapidly is not as helpful as you might think. Conversely the community has become much more accepting of it. I think this is the way a lot mapping ends up happening realistically. Stuff gets sketched from imagery, and then mapped in more detail on the ground later. When you look at developing world e.g. Humanitarian OSM Team activities, how to map a city rapidly / efficiently from the start, is still very much a pertinent and open question.
Mostly mapping around Central London. I live near Archway, but I tend to think about mapping whenever I am out and about anywhere these days. This includes various holidays and trips out of London. Places like Aberdeen, Nimes, Plymouth, Huddersfield, and (more ambitiously) Sao Paulo and Cairo
Creating open content map images for wiki projects, was my initial attraction to OSM. For example I'm a long time contributor to WikiTravel.org (user 'Nojer2') where we had extensive discussions at wikitravel mapmaking ideas before OSM came along.
OSM models itself on wikipedia in many respects. Since the big API 0.6 development push of early 2009, we now have Changesets with comments, which in turn gives us a 'history' tab, and a 'my edits' display. There's more work to do to make Change monitoring more useful and Change rollback more possible.
I've learned the basics of ruby on rails, and done some little bits and bobs in The Rails Port code including creating the 'history' tab for viewing changesets.
A while ago I made two little MediaWiki Extensions for OpenStreetMap, both of which are installed and running on this wiki, enabling you to embed a static map image or a slippy map into a wiki page here. That's in PHP. I have also experimented with Phprender and recently got OAuth working in php (need to publish that code somewhere)
I know java, and dabbled in JOSM coding to create the JOSM/Plugins/WayDownloaderPlugin. I also made an osmosis 'simplify' plugin (as part of the Waychains TIGER fixup) and I made a little java tool, tiletabber, for creating MapInfo .TAB files for tilesets
Also know a bit of Python.
In the interests of properly categorising myself...
...bit of lie actually. I know jack all Portuguese, but can quiz the girlfriend