Is there a market for my old slr cameras-all pre-digital?

Do my lenses adapt to a common popular digital box or should I unload the old stuff and buy a new DSLR. I hold pristine condition---Maxxum 7000 with AF 100-300, minolta---1.5 m / macro---with spare body---an x-700 / 2 x with 50 mm. & a Nikon EM with 1.8 x 50 mm

I don't know about adapting to a digital box, but I see cameras like yours are fetching around $100 second-hand http://www.vintage-point.info/vintage-search/?WBsearch=maxxum+7000+slr

So, I guess there's a market, but you probably won't get much for it…

Nikkor lenses will mount on Nikon dSLR's
Minolta auto-focus lenses will mount on new Sony alpha dSLR's

Which you choose will have to be based upon your needs.

Visit a camera store and hold both camera brands in your hands and see which one you like the best.

Your Minolta Maxxum AF lenses can be used on any Sony DSLR.

Your Minolta manual focus 50mm lens can be used on a Sony DSLR with an adapter.

Your Nikon lens can be used on any Nikon DSLR.

The market for used 35mm film cameras isn't very strong right now but they still have value. You can check used prices at B&H or Adorama or KEH and subtract about 35% from their price to find the value for your bodies and lenses.