Compass Security is a Swiss security firm specialising in ethical hacking and penetration testing. Amongst other offerings, they have a long list of freely available quality publications that present technical overviews of security attacks and tools as well as many other technologies from a security point of view. There are probably 100 or so articles published from last year back until 2004. I came across the site last year when I was researching USB security and found the Compass paper on U3 Insecurity.
Please note that some of the publications are in German only.