For value, it's hard to beat Southwest's Rapid Rewards. With double credit, you can fly 4 short and cheap round-trips (totalling $300 to $400) and get the virtual equivalent of a full-fare coast-to-coast US domestic ticket. The percentage value returned on your travel purchase is incredible.

If you don't normally fly Southwest, you can buy $16k of US Savings Bonds online using the Southwest Visa card and pick up a free ticket.

The Southwest tickets won't take you Europe or Hawaii, but they are very useful indeed for domestic travel in peak periods or on short notice.