I agree with the people simply suggesting a high-yield savings and rewards checking account. You don't have any worries about accessing money, and basically the same ROI. I use CapitalOne360 banking for my short term reserve needs. The checking is .20% for 49,999 and under, and .80% for 50,000 and over, and .85% at over 100,000. The savings account is .75%, period.
.75% is better than pretty much any CD's I could ever find, unless it was over 5 years. (I don't want to lock my cash away for that long.) But you'll never have any early-withdrawal fees. Which is what I like. Their customer service is excellent; I've never had any problems, and literally every service is free to use, and easy too. If you want more info, just ask.
If you want to use them, here's my refer a friend link:
https://r.capitalone360.com/fvMaBF6sbX If you open with $250 or more, you'll get $20 and so will I! However, don't feel like I'm pushing you towards my link. In fact, if you search on the MMM blog, he has (or at least used to have) an even better sign-on bonus. Either way, I suggest using a sign-on bonus, because FREE MONEY!