Thanks for the help guys! My 401k is invested 50% in a S&P 500 index fund (0.22%) and 50% in Barclays Aggregate Bond index fund (0.21%), is this good...
No, probably not, unless you're over 50.
The short, basic rule of thumb for bond allocation is 100 - age = stock allocation, so if you're 30, you should be 70% in equities, 30% in bonds. That's the basic starting point. As it seems you may not know that, then I would recommend you get started with
The Investor's Manifesto or the bogleheads wiki:
http://www.bogleheads.org/wiki/Main_Pagehttp://www.bogleheads.org/wiki/Bogleheads%C2%AE_investment_philosophyYou're going to want to learn a lot of things. Why you want bonds vs. stocks, investing policy statement, tax efficient fund placement(eventually), etc.
You're also going to want to ask yourself about your own temperament. The starting point of asset allocation is only that, the starting point. If you're scared of seeing losses then you may have to adjust it to be more conservative(more bonds), or if you're young and have years ahead of you you might want to go with more risk(more equities).
If as you dig deeper into the rabbit hole of financial knowledge you find yourself becoming more interested in it, you may want to examine further diversification and investment strategies(foreign stocks, emerging markets, small cap, REITs, etc.)
Welcome to MMM, and financial literacy.