I would not bring up non-permitted work if I were you. That will start a feud you don't want to get into since you, the neighbors, and the city will be duking it out. It's not worth the hassle. I think you can make major progress with asking for some quiet times though. Your neighbors might not realize how loud the hammering is. A nailgun might be quieter and a good investment for them. The outdoor saw during the big game might be really annoying so ask that they use it before or after the game. Just make it clear that you don't mind that they're working but want some quiet time to enjoy games, shows, reading, and other things rather than hearing hammering each day.

Personally, I'm very libertarian when it comes to property rights. I can compromise on the timing of things, but if you bring up the permitting stuff then we couldn't be friendly anymore. What one does with their property, time, and labor is sacred to people like me.

I've been on the other end of the issue.

While I like to think I demonstrated more sense about things than MrBaltimore's neighbor... it would be foolish to think that events like my Saturday afternoon into dinner time jack-hammering of the basement floor was met with joy by Al and his wife next door.

As this has been going on for so long without you doing anything I will base this on NOT wanting to directly confront them (which of course is exactly what you should do).

Download and print out in as official looking a font as possible the specific code sections that apply to after hours, un-permitted and un-inspected work; and throw in some data on the property insurance risks as well. Drop it into their mailbox and hope for the best.

Expect to need to confront them anyway.

Whatever you do, don't wait until you've had it up to your gills and go ballistic. That's what can happen when you've been understanding for so long.. and meanwhile, they just thought it didn't bother you. Choose a day when you're in a great mood and tip them off in a good natured way that maybe it's time to give you a break. It's heartwarming to see lovely old homes rennovated and admirable that they're DIY, but really... banging and stuff after dinner hour is really poor taste. DIY really must be for the weekend jobber.

If it bothers you that much, confront them when you're in a good and level-headed mood, as suggested by Lisa.

Personally, I think working until 10PM is acceptable for DIY jobs since most people are still up at that point. Any later than that, then that's a problem. If you can't hear the Ravens games b/c of the saw in the backyard, then either 1.) close the window, 2.) turn up the volume of the tv to drown out the sound of the saw 3.) go to one of the numerous bars around you and watch the game, or 4.) go to a friend's or relative's house to watch the game.

Actually it looks like the neighbors do not violate the noise laws - 10 pm is exactly the limit. See this link:
http://www.nonoise.org/lawlib/states/maryland/maryland.htm

I agree with others that the issue should be discussed in a friendly manner. Just explain your feelings and offer to work on a compromise. It is possible that the neighbors don't realize how much it bothers you.

If you're concerned about the permits, it might be a good option to bring this up in a conversation, e.g. "I love what you've done with your kitchen, was it difficult to get a permit?" or something along those lines.

P.S. That's why I want to live on a 3 acre estate. :)

They may not think that it is an issue because nobody has ever said anything to them. If you have a good relationship with them then you should be comfortable enough to mention that some of the work is becoming an issue, but I agree with everyone else, make sure you are level headed and polite because you still have to live next to them. If they don't stop then you can take further measures, but you should make them aware of the problem before anything else.

I note the 10pm regulation posted by Jelena. However, as a practical matter, I think it's a question of poor judgement and lack of consideration to neighbors to engage in hammering, drilling, etc past 7 pm, in a townhouse environment. Other regulations sometimes take adjoined structures into account... e.g. I believe there are regs against placing a piano against a common wall-- day or night!

I did a renovation myself, in an apartment, no less, and remember the enthusiasm and anxiety to get it done. But, frankly, I remember being too bushed to keep it up beyond dinner time. At a minumum, the quieter tasks, such as painting can take up the twilight hours.