I have an emergency fund of $10k in a money market account, about $3k for car maintenance and repairs (partly in the money market account, partly in a savings account), and then a "personal development" account of $2k (travel, expensive items, etc), which I keep in a savings account.
I'm leaning toward grouping these all together, or maybe only having one savings account with $1k in it and all the rest in the money market, at least earning me a little scratch every month. My preferred total would be $20k, which would allow me to survive a year of unemployment with no unemployment checks. I don't have any reason to believe I would be out of work that long, but you never know. More realistically, if something happened to my quality used car, I'd be able to spend less than half of it for another quality used car, have extra for any parts I need to change, and still have a 6-month emergency fund. I'm a bit risk-averse, but that's all a matter of perspective :D. I just feel that $20k is a benchmark that would make me happy.
For what it's worth, though, my 50% savings rate is all going to my 401k, to max that juicy employer match ASAP. Whatever I save above that goes to the cash bucket or is spent. I also deliberately set aside $100 every month for the car.