The Energy Project Blog (http://www.theenergyproject.com/blog) argues compellingly for 90 minute sprints as being the most efficient/effective.
The Four Hour Work Week (http://www.fourhourworkweek.com/) also suggests some other valuable time management choices - such as only checking your email twice per day and grouping all calls at the same time.
These ideas are not unique, not non-obvious and are not rocket science, but they are effective. Sometimes we just need to remind ourselves of the good habits we should adopt or resume.
The challenge is to think critically about all the ideas we encounter and consciously decide which are valid/good and therefore should be adopted - and those which are invalid and should be ignored.