Making a Digikey order; Any suggestions?

Looking at other ICs, I thought about buying one or two DS1307s, but 4 bucks seems like a lot to pay for something I have no current use for! Plus I'd have to get a batter + holder + crystal..

Are there any cheaper (Arduino compatible) RTCs available?

PS: What's the difference between DS1307 and DS1337 besides the price? They're both listed as I2C, but I swear one of them was SPI..

Ah, I think I've figured it out: DS1307 has no battery backup, but has alarms?