Real Estate has proven profitable for me. Look for cheap multi-family units. You could live in one-side rent the other for tax benefits, or rent both sides.

Stocks, bonds. 80% stocks, 20% bonds given your age and the fact you are already saving for retirement.

If you own a home, pay extra on your mortgage. Depending on how much extra, you could pay off your home in 5-10 years versus a standard 30.

Or you could use it for advancing freelance/etc. For instance, I pick up freelance web-dev jobs and do some advertising consulting with my background in the printing industry.

One last thing, still have fun with it. It gets easy to become so focused on investing that you are living for 10 years from now, and missing living-in-the-moment.