OTAs: May 21, May 23-24, May 29-31, June 4-7
Minicamps: May 4-6 (rookies), June 12-14
Here's more details on what can be done on these dates: http://www.hogshaven.com/2012/4/16/2951904/redskins-offseason-activities-begin-today-what-that-means
Also, the media will finally be allowed to visit the facility starting on Sunday, so next week we should start getting some more concrete info...and by concrete...I mean, optimism!
Fans of course can only visit during training camp and those dates will be announced in June.