Melissa hit on some great points. If you want in-depth info, Flyer Talk (a board like the DIS for travel) and various blogs (like The Points Guy or boarding area) can get you the info you want.
My take...
I started the same adventure a few months ago, looking to save some money for our annual pilgrimage to the Mouse. This is what I found regarding credit cards...
Basically, there are three types of travel related cards:
1) Those for everyday use (worth the annual fee)
2) Those procured and kept only for the benefits (benefits offset annual fee and are rarely charged)
3) Sign-up bonus (likely canceled just before the annual fee is due)
Many airline cards will generally fall within the second bucket. Spending on it will generate airline miles, but the
real reason to keep it would be for the benefits (better boarding time (i.e. room for carry-on), free baggage, in-flight discounts, etc).
Some airline cards even offer a companion ticket, which is basically a BOGO offer. Airlines that offer this option are:
Alaska: one $99 (+tax) companion
Delta (Gold card: one $99+tax; Platinum card: 1 free companion)
US Airways: two $99+tax companions
Other airline cards provide different benefits, like United Explorer provides 2 Club passes vice the companion fare, and American provides a 10% miles redemption refund option.
Some travel related cards fall into the first category. American Express Membership Rewards and Chase Ultimate Rewards provide points per dollar spent, which can then be transferred to several different airline and hotel partners. JetBlue, for instance, is a transfer partner for AMEX, thus a membership reward point can be transferred to JetBlue's frequent flyer program. These are valued in the "points & miles" community due to their flexibility. As mentioned, the Chase Sapphire Preferred is an Ultimate Rewards card, so it can transfer to Southwest and United (directly) or get flights with points via partner airlines (British Airways for American and Korean Air for Delta). The points also transfer into Hyatt hotels or Amtrak trains.
In addition, many AMEX and Chase cards provide a sign-up bonus (25,000 - 40,000 points) to get you started, once a minimum spend is reached. If the new Sapphire Preferred card holder spends $3,000 in four months, they get 40k bonus points for use on their partners, which may be a great way to get some free airline travel for everyday spend.
Depending on your travel habits,
consider a co-branded airline card only if you think the benefits of the card match or exceed the annual fee. For everyday spend to transfer to a favored partner, you would probably want to consider a card that has multiple partners for greater flexibility but also is linked to your favorite airline.
As Duds said, another great option is the Capital One Venture card. It gives 2x points on all purchases, which can be used to purchase tickets through the Capital One
travel agency. Of course, Membership Rewards and Ultimate Rewards have the same travel option with their points.
Personally, as DVC members, we travel to Orlando and Anaheim yearly (at least one if not both). Also, my parents live in Tampa, so travel to Florida from Oregon is almost mandatory each year. As such, we do travel a bit.
To make this less costly, I got the Delta Platinum AMEX, since the $150 annual fee is offset by the free companion tickets (starting after the renewal date and annually thereafter), free baggage, and priority boarding. It also allows us to purchase a Sky Club day pass for myself (with two companions or spouse and family) for $25, which will be handy for long layovers or when delays may cause the need for re-ticketing.
I also recently got the Hilton AMEX (no annual fee) to get 6 Hilton points on Gas, Groceries, Drugstore, and Telecom (phone/wireless/internet) to get a room at a Hilton in the Tampa Bay area (maybe on the beach!).
I also have a Green AMEX charge card ($85 annual fee) to save-up points for transfer to JetBlue (to Long Beach) or Delta (via Alaska to Long Beach or for travel to Florida). I can also top off my Hilton account with MR points.
However, I am thinking of the Chase Hyatt card ($75 annual fee), which has a bonus of two free rooms (again the beach!) with first use, an annual recurring bonus of one free room in a Cat4 hotel or lower (such as the Hyatt Orlando Airport), and no foreign exchange fees (good if we take a
Disney cruise). The Chase Sapphire Preferred is also on the radar, as it provides 2x points on travel and restaurants.
These are my thoughts and observations. Hope it helps, and good luck!