We've been using Maxim/Dallas DS1305/DS1306 RTC in many apps over the past 8 years or so. It works fine for us, and I've got all my proven "drivers" to set time, etc. It uses SPI interface.
A new design is on the drawing board. Does anyone have any compelling alternatives? Cheaper is better. ;) (lessee--DigiKey qty. 100 price is US$2.29) I prefer SPI 'cause I have the pins and I'm not a big I2C fan.
What is your favorite?