Easiest entry from the US side is thru Prairie Portage.  You will need an RABC as there is no Canadian Customs there. 

If you can't or don't want to get an RABC then you can enter either thru Saganaga or else thru Crane Lake.  If you enter thru Crane lake you will almost certainly want to use Anderson's (my recommendation) or Zups to tow you from Crane Lake to your entry point on the eastern end of Lac LaCroix

There are many excellent trip options from any of these starting points.  If you can advise more specifically as to the length of trip you'd like and how hard you'd like to work (plus what species of fish you prefer to catch) I'm sure that you will find plenty of route suggestions forthcoming.

If you are going thru Prairie Portage, Agnes is an easy lake to get to and has a nice mix of walleye, trout, and bass.  It also has some epic cliffs and at least 7 sets of pictographs that I know of, if you are into that sort of thing.  Downside:  It's big water and you will generally see people around, but not as bad as the milk runs in the BWCA.  If you do Agnes, you should either enter or leave thru the S-Chain and be sure you take a day or three in that chain to fish.  Most folks pass right thru in their hurry to get in or out of Agnes and that's a mistake.

If you want to see fewer people, take a tow from Moose Lake to Washington Island or Back Bay on Basswood and float the Basswood River.  The first portage is a doozy (1 mile) and there's hordes of people on the river sometimes, but once you finish the river, turn north at Moose Bay and head into Robinson Lake.  You'll leave the crowds behind.  From there, McIntyre for sure, and beyond that just as far as you want to go.  Brent, Suzanette, and Conmee all offer good fishing.  Or just stay on McIntyre if you're lazy...fishing is good there too.  Then work your way back down to Sarah (also a good fishery) and then out to North Bay of Basswood and back to Prairie Portage.

The Man Chain is also a good trip out of Prairie, or so I'm told.  I'll finally get around to trying it this year.  Head up thru Birch and Carp to the Man Chain and then round the horn at Saganagons and back down McEwen and a small chain of Lakes to Louisa, Agnes, and out if you are not averse to many portages but fewer people on the return leg.  If you want an easier trip, head up the border through Knife and Ottertrack and then loop back through the Man Chain. 

And that's just a few of the routes out of Prairie.

Out of Saganaga, heading up the Falls Chain to Kawnipi is very popular for good reason.  Fish in Kawnipi are plentiful and stupid. The main drag of Kawnipi and the lower ends of Kawa and McKenzie Bays see a fair number of canoeists but the other bays are equally good for fishing if not better.  Best campsites are in lower McKenzie Bay, which is a nice basecamp from which to explore the lake.  If you want an easy trip, head east on Saganagons and just base there and fish.  Very few people head off that way from what I am told and Saganagons has plenty of fish.

If you go thru Crane Lake, you really can't beat the Iron/Crooked/Rolands/Argo/Darky/Minn/McAree loop.  Spectacular waterfalls, great fishing, and some sweet pictos on Darky highlight the route. The tow is pricy, but worth it as the west end of Quetico sees fewer canoeists than the central and eastern regions.  Or just head up the Maligne River to Sturgeon Lake, or over to Poohbah. Sturgeon is a walleye factory and Poohbah has a nice mixed bag of fish.

Isn't there still a customs station on Sag for all the motorboaters?  I know it's a little bit of an extra paddle to get there but not too bad.

I can't speak to fishing but consider a Beaverhouse entry.  No rabc and you can pick up your permit day before. Large parking lot.  Instant solitude unlike PP.  All of snowdogs suggestions are great also - I've done them - and especially liked the Man Chain and back through McEwen and Louisa last July.  Saw no one for three days from Falls Chain to Agnes. Also from pp, route through North Bay and Isabella to Sarah and then maybe Conmee - Williams - Darky is hard to beat.

Wow!!! Some really great suggestions, thanks everyone. Keep them coming. Now if I can only get the weather to cooperate, and give me some higher water, few bugs j great fishing, and lower winds. I'll be ready to go. I have two Boundary Waters trips planned this year, and one to Voyageurs. Next spring will be my first trip into the Canadian wilderness, and I'm excited to try it. Thanks again.