I'm still investing in my 401K.
With the market dropping like it is, is this a good idea,or should I stop my contributions?
I'm in some fairly aggressive stocks. Does it make sense to switch to some more
conservative investments?

You should definitely continue investing in your 401k. Stocks go up. And they go down. That's just the way it works and always has worked. The stock market is a bumpy road to excellent long-term returns.

How much of your 401k is invested in aggressive growth stock mutual funds versus a balanced/growth-and-income fund or a bond fund really depends on how long you have until you plan to retire. Once you get within 10 years of retirement, I would definitely start rebalancing the portfolio away from aggressive growth and toward balanced/growth and income funds and bond funds. A helpful rule of thumb is that you should have your age invested in stocks and the remaining percentage in bonds. So if you are 45, you would have 45 percent of your portfolio in stocks and 55 percent in bonds. I would split the stock portion evenly between a growth fund and a balanced/growth and income fund. While this rule of thumb is a little conservative, in my opinion, it's a great place to start.

I hope this answers your question.

Whether you should keep investing is without question. There is a tax benefit to investing in 401Ks and IRAs. If you are uncomfortable being in risky investments, then move your money to a conservative fund like money market or cash reserves. You need to sleep at night. You can find out from your 401K adviser what they offer that has little to no risk.