The most recent report on Croatia's accession negotiations (from March 2, 2011) "On Reforms in Croatia in the Field of Judiciary and Fundamental Rights" can be found here:

http://ec.europa.eu/enlargement/pdf/hp/interim_report_hr_ch23_en.pdf

A timeline of key dates for Croatia's accession into the EU can be found here:
http://ec.europa.eu/enlargement/candidate-countries/croatia/relation/index_en.htm

The negotiation process is explained here: ec.europa.eu/enlargement/pdf/croatia/st20004_05_hr_framedoc_en.pdf

The European Commission periodically publishes an evaluation of Croatia's progress toward accession. The report includes analysis of the current political and economic status of the country and outlines the areas in which the Croatian government needs to focus on reform. Read the Commission's 2009 Progress Report for Croatia here:
http://ec.europa.eu/enlargement/pdf/key_documents/2009/hr_rapport_2009_en.pdf

The most recent Decision taken by the Council on Croatia's progress and priorities in the accession process can be found here:
eur-lex.europa.eu/LexUriServ/LexUriServ.do

Croatia's status in the accession negotiations: http://ec.europa.eu/enlargement/pdf/enlargement_process/accession_process/how_does_a_country_join_the_eu/negotiations_croatia_turkey/overview_negotiations_hr_en.pdf