From time to time you stumble over interesting types of documents of the EU institutions, such as the European Parliament Library Briefings.
One thing I’ve come across these days are the “Annual Activity Reports“* of the different directorates general (DGs) of the European Commission, i.e. the kind-of-ministries of the European Union. Now while these documents probably only give a positively-biased glimpse at what the Commission did in a year, they are (before the financial part) still rather concise documents and thus allow to see, for each policy-field, what were major issues over the last years.
Given the difficulty to get such an overview through other sources, this is probably a good way to start if one is up for some research into recent political developments at the EU level, at least from a Commission perspective, and starting in 2004, the year in which Barroso came into office.
* Update: For the older ones see here.