Depending on how much you want to spend, I would either look at a D90 or a D7000.
I’ve got a D80; the D90 is better, but not massively so. More of a ‘freshen up’ than anything groundbreaking over the D80. But, the D7000 is vastly better; faster with more autofocus points that come with things like subject tracking, faster frames per second for sports/action & the sensor is MUCH better, so you can shoot at low light with higher ISOs to retain a usable shutter speed & the noise levels will be kept quite low.
The D7000 is quite a bit chunkier than the D90, but if it was me, I’d be upgrading to that if the funds allow.