Southwest was available through Travelocity for quite a while, but they aren't anymore. They demanded to be removed from Orbitz because they found that Orbitz was giving bizarre routings that WN
didn't like. Though I've seen Orbitz give bizarre routings on other airlines too, such as MCO
I don't think we'll see Southwest or JetBlue on other travel web sites anytime soon, they're well known enough to do without it. It's also worth noting that neither airline has significant GDS participation... Southwest is bookable through Sabre only, JetBlue isn't bookable at all through a GDS.
Other airlines like ATA, AirTran, Spirit, and Frontier can be booked through the GDS and show up on various web sites.
David / MRY