The NFL released a list of dates for all teams' OTAs and minicamps. Teams are allowed to hold a rookie minicamp on one of the first two weekends after the NFL Draft and conduct one mandatory minicamp for veteran players.
Earlier in the offseason, on March 29 and 30 the 49ers held some OTAs. Going forward the dates are as follows:
April 30-May 2 (rookies)
What should be particularly interesting about these various OTAs and minicamps (except the first rookie minicamp this week) is what veterans will be absent. While players often are excused from some of these events, sometimes an absence is a sign of displeasure concerning an individual's contract status. There hasn't been much in the way of complaining thus far, but it's something to keep an eye on.