How can I run Bitcoind -server in "light mode"?
I don't think Simplified Payment Verification (SPV or "light mode") is available in the reference client. There are plans to implement it in the development going on in the discussion email list though.

However, you could download the source code for MultiBit and then use that as a starting point for your own daemon. Alternatively, just use the underlying BitcoinJ library which offers some example tools that probably do what you want right out of the box.