For example, I'd like to use getblock, getrawtransaction, etc but not having to get the entire blockchain....
Don't think that would be possible, since RPC commands refer to a local database... which is the blockchain.
If it's time rather than HD space you're trying to save, you can use the existing client to seed the new one:
./bitcoind -connect=x.x.x.x -listen=0
(where x.x.x.x is the IP of your existing client)
Be aware that it can take a bit of time to verify every block, as I mentioned earlier in this thread.
You can also try copying the block database - it should be binary compatible across platforms. Basically, copy the contents of directories blocks/ and chainstate/ from your existing data dir, to the data dir on your linux box, then start bitcoind.
Another option, if you really don't want the duplicate blockchain, may be to use the API of a block explorer?