Oceanic Airlines Planes
In 2x17, Locke goes to meet with his father at a motel by the airport. When he goes in, an Oceanic plane flies overhead. Then, when Helen drives off, another Oceanic plane flies overhead.
Sayid - Locke Connection
In 2x17, Nadia is a customer of Locke's. She is buying a house in LA, and Locke inspects it.
In 2x17, we see that Locke has yet another job. In this flashback, he is the owner of a home inspection business named WELCOME HOME.
Henry Gale's Drivers License
In 2x17, Sayid shows Henry Gale the license of the real Henry Gale that was buried in the grave. The real Henry Gale is indeed from Minnesota - but he's also black, so, our Mr. Gale is a FAKE!
Blast Door Map
In 2x17, a map of stations is revealed on the blast door via an ultraviolet light when the timer counts down.
You can make out "I AM HERE" with an arrow pointing to the SWAN STATION. You can also see the medical station logo, and some new logos that are hard to decipher.