You don't qualify as an accredited investor with only $450k of savings, so you won't be able to angel invest or invest in SecondMarket shares.

Start off by contributing the maximum amount to a Roth IRA every year, even if it's just for the tax deduction.

Personally, after that I would put about 25% into a no-load index fund, and the rest into high-interest savings (like ING Direct). I would optionally invest no more than 10% of my savings in speculative stocks.

The nice thing about this setup is you can make a decent compounding return with your index fund and you won't lose the farm if it tanks, but the majority of your money is immediately available in case you need it for your side projects or just want to blow it on a vacation (and you won't have to pay the higher taxes for cashing out stocks early). If you don't need it, it's at least not sitting around doing nothing.