Still a little moody from the Monday blues? Split up your busy Tuesday with a much-needed breather among the stillness of bookshelves and the common understanding of moms, dads and nannies at Big Blue Marble Bookstore. Blue Marble Babes is a casual weekly playgroup that gets going when people drop in at about 10:00 A.M. and usually lasts until the little ones start demanding lunch. Toddlers can meet new friends or read books while babies snooze and caregivers discuss anything from the frustrations of the terrible twos to the state of the world today. Grab a cup of tea from the upstairs café and check out the extraordinary Big Blue children's section with your ankle biters. Spend your cash on the books; this playgroup is free.