can anyone recommend a easy to get site ( public transport) to hike outside Madrid? Or do you know of any organizations/outdoor adventure tour groups that arrange hiking excursions?

There are a few web sites that deal with hiking in the Madrid area (I hope you can read Spanish!):

http://www.geocities.com/senderismo_madrid (click the topmost link on their menu for a links to hiking info for the Greater Madrid area).

http://www.andarines.com/madrid/

http://www.guiamadridrural.com/SaberMas/Senderismo.htm

I haven't used these sites, so I can't vouch for the currentness or accuracy of their info.

There's also a hiking discussion forum on the Spanish web site Viajar.com (part of Ya.com): http://foros.viajar.com/jsp/JVforums.jsp/=readforum=31775=0=1

¡Buen viaje!

The easiest places to go hiking from Madrid are Cercedilla, Cotos or Navacerrada, you have a train each hour, to go to Cotos or Navacerrada you have to change the train in Cercedilla, and to hike in Cercedilla you have 20' from the train station before you leave the road. If you're going in winter you have to be carefull with the snow or the weather.
If you prefer to go with a group, check here also
http://www.arawakviajes.com/home/home.htm , prices are not expensive, they take you in a private bus with one guide or two depending on how big is the group, normally from 20 to 40 people, you can choose between different difficulties, or harder routes....

Hi,
I can highly recommend the group Tierra de Fuego. They have a shop on c/Pez, (I think the nearest metro is Callao or Noviciado) where you can pick up a leaflet with info regarding the hikes. You can choose from 3 different levels depending on how experienced you are, and there is also an alternative for us that can't get out of bed early - the bus doesn't leave until 10! (normal departure time is 8 - 8.30)

The price is 16 euros per person which includes transport, insurance and two guides per group. You bring your own lunch, and water and stuff as well.

We went on a walk with this crowd two weeks ago and will be going again this weekend. The guides are really nice and will tell you a lot about the area if you ask, but they won't be "babysitting" you - it's all very nice and relaxed, and not too much of "let's all look at this together".