Some introduction to HEP, ATLAS, the Higgs... and even the tau lepton !
To discover ATLAS the first pages to look at are obviously the ATLAS collaboration public page and the CERN public page. However, a selection of videos and links is also available on the ATLAS-LAL group outreach page.
A glossary of the particles names and features can be found in the special edition prepared by the Science Magazine about the Higg Boson discovery (Science 21 December 2012, Vol 338 no. 6114 pp. 1558 to 1582).
Outreach material is prepared by the International Particle Physics Outreach Group. A popular introduction to HEP, called "What does a Higgs boson eat during the winter and other essentials details", is here
The Summer Student Program provides every year introductory courses on all the aspects of HEP. Participants to the Challenge can learn here how we go from raw data to Physics results and why the program which produced the events used in the challenge is called Monte Carlo.
Those of you who want to explore further the methods (and vocabulary !) used up to now in HEP can start with the School Of Statistics web site, which provide courses, contacts and references. Here are the open access proceedings of the last edition.