To download the blockchain with maximal speed you want to be connected to nodes with high bandwidth.
On default bitcoin will search and connect to random nodes. One can add nodes to bitcoin conf to tell bitcoin to connect to specific nodes.
To add a node to the bitcoin client to connect to, add the following to the bitcoin.conf file in:
Windows:/appdata/roaming/bitcoin/bitcoin.conf
Linux: $USER/.bitcoin/bitcoin.conf
ADD THIS TO BITCOIN.CONF
addnode=127.0.0.1
To find high bandwidth nodes go to:
blockchain.info/hub-nodes
for example and browse the hub nodes section. It is not required to add the node port, bitcoind will find the correct port.
.... Enjoy downloading at full speed.
EDIT: since the question / answer gained such an attention i decided to make this a community wiki :)