I paddled the Rivanna River from Crofton to Palmyra 2 weekends in a row. The first weekend I started early Sunday around 8 am. The water was nice and clear saw several fish, two deer, and a few hawks. This is very nice stretch of river that the Virginia DGIF says is about 6.5 miles. It took me 2.5 hours and 2 hours respectively from put in to takeout, so this is a relatively short paddle that's doable on weeknight as we head into the longer summer days ahead.
There are just enough riffles in this stretch to keep things interesting and while the DGIF says there is only one class I-II rapid there are probably three or four other spots I'd classify as class I or less that make the journey a little more fun than a straight 6.5 mile paddle on a flat river. There are some nice beaches and stopping point through this stretch if the water isn't too terribly high (>4ft).
Parking concrete ramp at put in.
Parking and gravel ramp at take out.
Put in is on state route 600 in VA as it crosses the Rivanna.
Take out is on Union Mills Rd basically behind two j's barbecue (excellent food btw).
DGIF link for Rivanna put-ins and take-outs: