I had a look at the Isle of May blog for July 30th last year and it appears that there were still some Puffins on the island, so a boat trip out from Anstruther may be worth considering to try and see Puffins, but the earlier you go the better the chances. Guillemot, Razorbill, Kittiwake, Shag and Cormorant are also possible on the island, though numbers decrease as the breeding season ends.
Other places possibly worth visiting include Fife Ness (seabirds passing close offshore - Skuas and Shearwaters possible in small numbers, Terns, sea Ducks, Gulls, and possibly Divers).
Vane Farm/Loch Leven RSPB reserve offers a range of species although mid-summer possibly isn't the best time to visit.
Loch of Kinnordy (near Kirriemuir, north of Dundee) can be good for Marsh Harrier and Osprey in summer, among other things.
Montrose Basin, northeast from Dundee on the coast, has a mixture of waders, waterfowl and terns (Common, Arctic and Sandwich) at that time of year.
There is also a small Puffin colony nearby at Auchmithie, though these may well be gone by the time you are in the area. The Angus Glens can be very good for Red and Black Grouse, as well as raptors, Ravens, Ring Ouzel. Dotterel and Ptarmigan are possible at the tops of some of the higher mountains in the area.
I think Oban harbour can be good for Black Guillemot. White Tailed Eagle could turn up almost anywhere (a 5 year east coast re-introduction programme ended last summer).
There are lots of other areas that are worth a visit, depending on the amount of time you have, that may not have too much "new" on offer but are worth visiting anyway. If you have internet access it may be worth asking in here for recent sightings in the area while you are here, just in case there is a rare bird or two around.