The later version of Todd Rundgren’s band Utopia had four members who were all lead singers and songwriters - Todd (guitar), Kasim Sultan (bass), Roger Powell (keyboard) and Willie Wilcox (drums). Each would sing lead during the same album or concert or even the same song. On the song Love Alone (written by Sultan) they would even do barbershop harmonies.
Little Feat. In the heyday, Paul Barrere, Sam Clayton, Lowell George, and Bill Payne all took turns on vocals.
And Ace and Peter sang lead on some of thier most famous songs. Peter scored thier highest charting hit with Beth pretty much without the rest of the band.
In the original lineup of the Stranglers, lead vocals were shared between bassist J.J. Burnel and guitarist Hugh Cornwell (plus the occasional contribution from keyboardist Dave Greenfield). When Cornwell left the band, he was replaced by both a guitarist and a full-time lead singer, and Burnel contributed fewer vocals during those years. Now they’re back to the quartet format with Burnel and current guitarist Baz Warne sharing lead vocal duties.
Just to answer “what’s going on with them now”: Styx still tours, pretty much all the time – in the past few years, they seem to do a joint tour with another classic-rock band or two in the summer (I saw them with Boston in '08, and with Kansas and Foreigner in '10), then tour on their own in the winter. They replaced DeYoung with a Canadian keyboardist, Lawrence Gowan, but Tommy and JY are still with the band (and, really, the two of them seem to be the ones in charge).
When they perform, they almost exclusively play their 1970s - early 1980s stuff; it winds up being about half Tommy on lead, with Lawrence doing most of the rest, and JY singing the songs that he sang in the first place (like Miss America and Snowblind).
They haven’t issued an album of original music since Cyclorama in 2003 (shortly after Gowan joined the group); on that album, Tommy sang most of the leads, followed by Lawrence. In 2005, they released an album of cover songs – that one, too, had a similar breakdown of lead singing (Tommy, then Lawrence, then JY).
Barenaked Ladies, until the recent departure of Steven Page, had two vocalists: Page and Ed Robertson.
311: Nick Hexum and SA Martinez
Devo: Usually Mark Mothersbaugh or Gerald Casale, occasionally Bob Mothersbaugh.
ZZ Top: I think it’s mostly Billy Gibbons, with a good chunk by Dusty Hill.
Pink Floyd: Waters and Gilmour, and Waters and Barrett back in the day, with Wright once in a while. Don’t know if Mason ever sang lead.
Hawkwind: Brock, Turner, Lemmy, et. al.
Journey famously got a new lead singer from a YouTube video, Arnel Pineda. Virtually indistinguishable from perry, imho.
A lot of 50s groups changed lead singers and often entire memberships. One member would own the rights to the name and replace members as needed.
The pussycat dolls change leads every few years.
Depeche Mode. Usually, David Gahan sings the fast songs, Martin Gore sings the ballads. The formula has become a little jumbled as time has gone on but it’s still generally true of their catalog. It’s amazing how many people genuinely can’t tell the difference as to who is singing what song sometimes, though.
Along with the occasional song by Ace Frehley & Peter Criss.