Introducing appointment slots in Google Calendar
gmailblog.blogspot.com
gmailblog.blogspot.com
I still use Google Calendar because it's the best (and just about the only) free, web-based offering, but I'd love to hear about alternatives.
That makes for a really poor UX for them, so I'll definitely be interested to see how Google's new appointment slots work.
I use Google Calendar's event scheduling feature a lot, because I often need to schedule group meetings. But when the participants I need to invite don't have a Google account, I use Doodle.com, because it has a free version that doesn't require everyone to register with it (low barrier to entry).
Of course this won't have enough features to compete with all the products, but for a SMB with relatively low number of employees it's quite possible than they go to Google first.
I would check out OHours, its actually been a pretty neat way to to set up office hours for myself and allow others to sign up and come meet me. http://ohours.org/