I use this u-lock and back it up with this chain in combination with this mini u-lock. The chain is very heavy, and while I can wrap it around the seatpost for transport, I prefer to leave it locked up to the rack at work. When I'm on the run I back up my primary u-lock with this cable lock.

Transporting the my big, heavy u-lock has been a thorn in my side. After much research, including a thread that I started on this sub-forum, I came across what I thought was an elegant solution... the Abus UGH 02 bracket. I couldn't source it locally, so I ordered it from Wiggle in the UK. It was pricey, but hey... I'm worth it!