If you have time Moosehead Lake is gorgeous, it is about 2 hours from Bangor (probably less if you have directions, we didn't). The drive is pretty boring.
If you are in the Bangor area (well this is actually in Brewer), there is a restaurant called the Eagle's Nest. It is small, but wonderful.
Just an FYI, Acadia will be PACKED over Memorial Day, as will Bar Harbor, parking there is at a serious premium. There's an ice cream shop called Ben and Bills that has lobster ice cream (which is okay), and amazing blueberry gellato.
There is a sardine and blueberry museum east of Bangor, and north of Ellsworth. I couldn't tell you where exactly.
I split my time between WI and Bangor. There is definitely a lot more to do when it is warm out.