Cushingham...

What are the rules on investing in IRA's and/or Roth IRA's while contributing to a 401(k)? Can I do both?

The general answer would be yes. You can find more detailed information from this Fairmark Press Site dedicated to Taxes and Investing:

http://www.fairmark.com/rothira/rothvemp.htm

Another good site from Morningstar.com on 401k's:

http://news.morningstar.com/doc/pfarticle/0,,4307,00.html?etfsection=Centers1

One generally accepted approach to this would be to:

1) Contribute to your 401k up to the point of maximizing matching funds. (This is free money that a person would be foolish not to take. Not all employers have a matching program and those that do are not all the same).

2) Next, contribute to an IRA. (Whether Traditional or Roth is a personal decision. In my opinion, the Roth IRA is much more versatile. Something you need to study up on before making a choice). This little calculator may help in making a decision:

http://www.calcbuilder.com/cgi-bin/calcs/IRA1.cgi/themotleyfool?Question=Income

3) Thirdly, if you still have funds to invest after maxing out your IRA...contribute to your 401k up to the allowable limit.

4) And finally, if you have additional money to invest after all that - begin a taxable account with a reputable discount broker such as Scottrade.

Hopefully you have a variety of good funds to select from in your 401k Plan. Passively managed Index Funds with broad market exposure, low expense fees and no-loads, in or out of the funds, would be ideal.

Determining your asset allocation should be at the top of your list of things to do as well. A well diversified portfolio can do quite abit towards reducing the risks associated with investing. A Total Stock Market Index Fund, such as the one offered by Vanguard (VTSMX) would be a good "core" fund to start with.

http://flagship3.vanguard.com/web/planret/PTRetireCenterOV.html?type=PIWANTTO7

I wish you well...

Bill