Keep it where it is. The additional interest you'd earn isn't worth the risk. Example:
Let's say you've got $30,000. Right now, S&Ls are paying about 1.5% per annum. That's $450 a year, or $37 a month. In 4 months, that'd be $148; in 6 months that'd be $225. Agreed, that's pretty paltry.
Suppose you put the money into a mutual fund. Let's say Fidelity's Massachusetts municipal bond fund. FDMMX. During the past 12 months, it's had a 13.6% rate of return. Sounds good, and it is. That'd be a return of about $4,200 in a year. Or $1,400 over 4 months, or $2,100 over 6 months. Still, over a 4 month term you're only talking about a difference between that ROI and the S&L rate of $1,175. But the big point to remember is that funds--including bond funds--can decline in value. The value of a bond drops as interest rates rise. And most people expect interest rates to rise. Over the past 3 years, that fund has return 3.68% annually. If it performs in line with its 3-year average, you'd earn $368 in 4 months, or only $120 more than keeping it in your savings account.
And if the fund declines? In the past 3 months, that fund's cumulative return has been -0.88%. So if you'd put $30,000 into the fund 3 months ago (excluding any expenses), you'd have lost $264.
And there are plenty of other examples of drops even in an up market. Fidelity Spartan Long-Term Treasury Bond Index Fund--1 year return -13.41%. And there are many, many more.
So, you might end up a few hundred dollars ahead. But you could as easily end up a few hundred dollars--or even more--behind.
Don't do it. It's not worth the risk. Keep the money just where it is.