The bogleheads forum is ok, but it can be overwhelming at first. I'd say start with a book from the library on personal finance. Anything by John Bogle or the bogleheads is probably good. I liked "Random walk guide to investing" and "I will teach you to be rich" (aimed at 20 somethings, but still relevant).

Both PPs gave helpful advice. Vanguard has funds that will mix stock and bond indexes too (both static and lifecycle).

If you're okay with stock market risks, just buy one of the Vanguard's market index funds. It's the cheapest in expense ratio.
Over 90% of the actively managed funds do not outperform market index on a consistent basis. It'll would be awfully hard and risky to try to pick the rest 5% or 10%.

Go to bogleheads.com and read the wikis. thank me later.

http://www.bogleheads.org/wiki/Asset_Allocation

I have some money in savings that I'd like to invest in mutual funds, but I am completely overwhelmed by everything out there and don't feel like I have a great grasp on how to make sure I have a well-rounded portfolio. I have a 401k through work, so picking those investments was easy, because we are limited in what we can choose from, but for a separate, non-retirement account, I don't know where to begin. How do you decide what to invest, how much, and how to split money between different mutual funds? Thanks!