The third round of Tube strikes has just begun, running from 7pm this evening with services likely not returning to normal until Thursday morning.
According the TfL, around 40% of services ran during the last strike. The RMT and TSSA suggest that the figure was far lower. Regardless, expect the same level of service for the next 24 hours. TfL are laying on 100 extra buses and increased riverboat services in order to keep London moving.
Once again, I point you to the excellent interactive Tube strike crowd map. Updated in real time by real - frustrated - travellers it's a great guide to getting around, or spotting where you're likely to grind to a halt.