You could follow Pedaling Walrus' route, but continue up to Burlington. There you can pick up the Cross Vermont Trail. It is a rail trail, meaning shallow grades in general, that runs across, roughly paralleling Route 2 and/or 302. It ends up in Waits River, on the banks of the Connecticut. Woodsville, NH lies just across a very rideable little bridge. In Woodsville, if the idea appeals, you can access the Cross New Hampshire Adventure Trail (XNHAT) which runs across the state just North of the White mountains, to Bethel Maine. Each of the cross state routes has a website with maps, cue sheets, updates, pictures, etc. Since they are on old RR rights of way, they are very flat, with occasional hilly road sections.