Safety is one of my favorite topics, not only because it’s important, but also because there is always room for improvement. I collected five links for you, which all provide good safety-related content. Enjoy, and feel free to add more links of you own in comments.

Lessons Learned, by FAA
If you like the “I learned about flying from that” column in Flying magazine, you’ll enjoy this new website from the FAA, which contains several analysis based on accident reports. The website organisation makes it much easier to read than a standard, linear report.
http://accidents-ll.faa.gov/

Online safety workshops
The next time weather will make flying impossible, visit this website, and complete one of their online workshops. Recurrent training on the following themes are available:
Single Pilot IFR - IFR Weather & Planning – Mastering Approaches – Airmanship – Safety – ATC Communications – Risk Management – Non-Towered Airports – Night Flying – Accident Analysis – Quizzes
http://www.pilotworkshops.com/

AOPA on mid-air collisions
Unlike other hazards, mid-air collisions are not situations that one can recover from. At least I beleived so, until I read more about them. This page from the AOPA also contains further documentation about mid-air collisions, and their prevention.
http://www.aopa.org/training/articles/2008/080521pilots.html

UK Airspace Safety
The UK airspace can be dense and busy. The Airspace & Safety Initiative is a joint effort from several state and privage bodies to investigate and tackle the major safety risks in UK airspace. Parts of it are only UK relevant, but most of it is applicable worldwide.
http://www.airspacesafety.com/content/links.asp

English vs. French at Paris Charles-de-Gaulle airport
The last one is a perfect example of the importance of proper phraseology for ATC communication. For years, Paris Charles-de-Gaulle was operating in both French and English. This was a mark of french protectionism, but it lead to several problems… When english finally became the sole standard, it was not without difficulties…
http://marcschoenfeld.com/airfrance.htm