I've got an OpenGL game (well start of one) where my objects
very considerably in size. I realize that OpenGL itself is unitless
but my game's units can vary from anywhere between 10 feet
for small objects up to 1,000 feet for the largest.

Currently my textures are typically of 512 or 1024 pixels.

The small objects are rendered very nicely, but the large objects
are scaled up quite a bit.

When I zoom in, the small objects look great, and the large objects
look jaggy; or at least their outlines. I changed to a multi-texuture
strategy where as I painted on a texture over the non-alpha part of
the scaled up texture.

Are there any strategies that I can use to get "crisper" looking
large objects. Not looking for details. Just generalties.

thanks

Detail texturing is always a good move. Create a low-frequency texture that adds detail to your objects, add it as a separate texture pass (or use another texture unit) and render it when the camera gets close enough. The trick here is to apply it at an angle, so rotate your texture matrix a 20-40 degrees. This breaks up tiling and makes the trick less obvious.