Mike's Bakery of course. I've heard there is a better, less touristy option, but can't recall the name.
Sheila
Modern Pastry is slightly better, but smaller
http://www.modernpastry.com/ I work at Government Center.
If you go to the north end for lunch M-F between 11 and 3 try La Famiglia
http://www.lafamigliagiorgio.com/ they have a sampler it's under $8 and comes with 5 things that are different each day. You can get any or all of the 5, I'm usually not sure about one or two of the 5 things, but I get them all and usually find I like those ones the best. (Except the pesto, I don't like that)
The Duck Tour is the best of anything in Boston. Every city has one but the one in Boston is the best, There are some "fakes" but
http://www.bostonducktours.com/ is the one you want.
As someone who works in Boston, I like the New England Aquarium, though I have been to many better. I work at a training center that people come to from all over the country and if you go to the Aquarium in Atlanta, Baltimore, Cincinnati (Newport Ky) etc, SKIP the one in Boston you will be disappointed.
The saint Patrick's Day Parade is in South Boston on March 18th.
http://www.southbostonparade.org/ I have friends who will be marching in Star Wars costumes in that parade. (501st Legion)
Plymouth Plantation is nice, I should go there I haven't been in YEARS, Salem is an interesting city especially if you have any sort of affinity to Pagan spiritualism. The witch trial didn't involve witches but the city now has many shoppes that sell wands and crystals, herbs and potions. It also have a lot of small museums, like a pirate museum and witch museum. The Peabody Essex museum is also there.
http://www.pem.org/
Victoria Station is one of my favorite dining locations in Salem, though there are many others. Nathaniel's at the Hawthorne hotel is good, but high end, thought the $25 333 special sounds like a great deal.
http://www.victoriastationsalem.com/
http://www.hawthornehotel.com/dining/
Boston is My city and if you want to know anything specific PM me.