I've always thought it would be nice if you could cause Ruby to dump its heap and symbol table to a file, which could then be loaded by other instances of Ruby. So, for example, you could run Ruby, load all of the Rails files, and then save everything, so the next time you want to run Rails, you just have to load one file instead of hitting the file system 2000 times.

You could probably also do this by running a Rails instance as a service, and then every time you want to run Rails, you tell the service to fork, and use the forked thread. I think this is how Passenger works actually?