Portland, like any other town, has the chain breakfast joints like Denny's and Friendly's where you know exactly what you're gonna get and how much it will cost.  But if you want to try some local flavor, there are a bunch of great breakfast places to check out.  Marcy's, on Oak Street in town, is a cheap greasy spoon with young, sassy waitresses and old Italian men filling the booths.  Portland Street Diner, on Portland Street, is a fairly new place, a little more on the expensive side because they serve items like crab and asparagus omelets, and they bake their own bread daily, which they use for their toast, and you can buy it by the loaf.  If you want something more upscale, try Bintliff's, also on Portland Street, in an old purple house.  More expensive, but you definitely get what you pay for.  It's an awesome place for brunch, especially if someone else is paying.  There's also the Breau-Lu Cafe (short for BREAkfast and LUnch Cafe) on Forest Avenue, a couple miles out from town, which I hear is very yummy.  About a mile down the road from there is the Bayou Kitchen, which is a tiny little place with a Louisiana feel and the kitchen right behind the ordering counter.  They have the best pancakes in town, their most famous variety being Ginger-Blues, a stack of ginger and blueberry pancakes, plus they have some real crazy southern varieties of eggs with all kinds of hot sauce.  Of course, there is always Becky's Diner down on Commercial Street, and you'll see their bumper sticker on every third car around town.  They have all the typical stuff, but I bet you can find a place cheaper with a shorter line and still be more than satisfied.  As for coffee shops, there's a ton of places on Congress Street, including Starbucks, Coffee By Design, and Zarra's.  Also recommended are Acoustic Coffee on Danforth Street (live music in the evenings), and pretty much any place downtown is good, especially Breaking New Grounds on Exchange Street.