This small hint may be of some help when you have to reinstall Lion from a recovery partition in a network environment that does not have an active DHCP server. In this case, a small intervention in the Terminal is required.

Once you've booted into the Recovery partition, open Terminal by clicking its icon in the Utilities menu. Then:

• Get a list of the network interfaces for the Mac you are installing Lion on:
  
  networksetup -listallnetworkservices
  
  
• Set up the network interface, as listed by the output of the command mentioned above (Ethernet or otherwise):
  
  networksetup -setmanual {INTERFACE NAME} {IP ADDRESS} {SUBNET MASK} {ROUTER}
  
  
• Set the name (DNS) servers:
  
  networksetup -setdnsservers {YOUR DNS SERVER}
  
  
• Verify that the changes have been correctly saved:
  
  ifconfig
  
  Examine all the entries and find the one you have actually worked on (ex. en0 is generally, but not always Ethernet).
• Quit Terminal and continue with your installation by following the onscreen steps.
• Wait for the download to finish.
• Enjoy your freshly downloaded Lion!

[crarko adds: I haven't tested this one. The man page for networksetup provides more information on the available options.]