We've got an assortment... IRAs, 401k, regular savings account, stocks. I have it setup so that a certain amount is automatically deducted from my checking each month and put into my IRA. It makes it easier for me to keep contributing. I've done CDs in the past because I needed something for the short-term that was low risk, but higher yield that the current savings account interest. We've also invested in T-bills. The nice thing about those is that you don't pay state tax on the interest.
For those working at steady jobs, I'd definitely take advantage of the 401k plan--especially if they do company matching. They will usually have tools that will figure out how to best diversify your investments within the plan so that you can better maximize your return based on your present retirement goals.
One other thing to consider is a whole life insurance policy. These policies are best purchased the younger you are. You pay into them for a minimum of so many years (usually 10 years) and then after that you can just let the policy accrue in interest. One nice thing about those is that you have the option of taking out a loan against the policy that is interest-free, if needed (you basically can make a loan to yourself). We're considering getting one for our baby after she's born just so she has something available to her if she needs it down the road.
Whatever you decide, make sure you fully understand the risks of the investments and be sure you are okay with whatever percentage possibility there is of losing the money.