Registration deadlines have passed in most states but California, Colorado, Connecticut, DC, Hawaii, Idaho, Illinois, Iowa, Maine, Maryland, Michigan, Minnesota, Montana, Nevada, New Hampshire, New Mexico, North Carolina, Utah, Vermont, Virginia, Washington, Wisconsin, and Wyoming — have some form of same-day registration (in North Carolina, same-day registration is only available during early voting. Alaska and Rhode Island allow same-day registration, but only to vote for president and vice president; in RI, you have to go to the office of the Board of Canvassers; you cannot do same-day registration at your polling place).
No ID is required in California, DC, Hawaii, Illinois, Maine, Maryland, Massachusetts, Minnesota, Nevada, New Jersey, New Mexico, New York, Oregon, Pennsylvania, and Vermont. IDs are required in the remaining states; Ballotpedia has a detailed, state-by-state list of what IDs are accepted. Almost universally, you'll need to present ID if you're doing same-day registration.
More voting information and resources here.