See the full post here for more info, including client releases: London Mainnet announcement If you are running Eth2 validators, you must also update your Eth1 nodes! If you are just a user of the network, you don't need to do anything or update anywhere - anyone asking for your wallet information to prepare for London / 1559 is probably a scam.
See a countdown here.
EthCatherders London Community Call: Aug 02, 1400 UTC
EthStaker live watch call: Aug. 9:00 UTC "livestream we’ll be having a POAP.art London-themed Painting Party, multiple POAP distributions, a POAP.fun raffle, and special guests!"