It is hard to keep track of all the trade restrictions, trade exceptions, and the dates that surround each. I thought I'd provide a list and brief explanation of each here.
The Celtics signed Marcus Smart and James Young on July 10th. Draft picks that are signed cannot be traded for 30 days after they are signed. In case you are wondering, both our rookies can now be included in trades.
There's also a timeline restriction on Marcus Thornton and Tyler Zeller. Either one can be sent out in a trade by themselves at any time. However, if the Celtics wish to package them in a trade, they'll have to wait until Sept. 10th (two months after the trade from the Nets was made official) to do so.
Finally, Avery Bradley was re-signed as a free agent, so he's not eligible to be traded at all until January 15. Same goes for most free agents signed in the offseason.
The Celtics have 3 Traded Player Exceptions (though one of them is probably useless).
Fab Melo: Remember him? We traded him before he washed out of the league, so we can use a TPE generated from that trade of a whopping $283,816. I don't that can even be used since the smallest contracts in the league are way above that range but if you are curious, it expires on Friday (8/15).
Courtney Lee: He has a trade exception of $2.09M expiring on 1/6/15. That might prove useful at some point, especially if the Celtics can create some room under the luxury tax threshold.
Kris Humphries: This could be a useful one. The TPE is for $4.25M and doesn't expire until next summer (7/19/15).
It is worth noting at this point that Evan Turner has not officially been signed by the Celtics, though reports indicate that he'll make a portion of the MLE.
The Celtics will have the rest of the MLE (whatever is left of the $5.3M) and the Bi-Annual Exception ($2.07M) that they could use on free agents, but I'm guessing that unless further changes are made they'll elect to not use them.
We're expecting the NBA schedule within the next week or so, and we'll look at those dates in detail as they become available.