Maybe an alias... There's no directory presets path in the preferences that I know of. Animation presets are not necessarily compatible with different versions of AE so some care will have to be taken there.
I have an alias to a bunch of expression presets that I have collected over the years. It works just fine across the AE versions I have on my main work station and my laptop. The Alias is in the ProgramFiles(Applications)Adobe After Effects CS6 (version)/Presets folder. My custom presets are stored in a shared dropbox folder so that every machine that's synced to the dropbox folder has access to all of the custom presets through Bridge or through the Effects and Presets Panel.
Aliases will work fine on Mac, but not necessarily will links work on a Windows machine. There I'd rather define a group policy to define a custom My Documents path or even map a network drive....
We run about 20 Windows machines and I want to be able to put all of the presets on one place on our network that all the computers can look to. So when we add more we dont have to add to every computer everytime. I guess I would need some file in the presets folder redirecting to the network location?