To further drive home what Otto Rahn has mentioned, I'm a huge fan of Matthew Reilly, James Rollins, & Steve Berry.
Matthew Reilly is who really got me into reading adventure novels. Check out Temple & 7 Deadly Wonders (one of my favorites).
James Rollins is by far my favorite author. Excavation is heavily into archeology and lost cities/traps/etc...very Indy-ish. Sandstorm is the same. His newer books are a little different, but also great...a little less adventure, a little more action.
Steve Berry is also one of my favorites. His writing style is top notch. He's more along the lines of Dan Brown, though, than Indiana Jones. Alexandria is a very, very good book.
I've also read David Gibbin's Atlantis...it was ok at best to me.
Elizabeth Peter's Amelia Peabody series revolves around Egptology and archeology.
Wilbur Smith is another great adventure author. A great recommendation for Indy fans.
Robin Cook usually writes medical novels, but ventured into the adventure genre with Sphinx.
I'm not really a fan of Clive Cussler, but Inca Gold was ok.
J.F. Freedman's Fallen Idols was a fun read.
And I'll save the best for last, Tim LaHaye's (author of the Left Behind series) Babylon's Rising series. It's a religious apocalypse series like Left Behind, but it's done in a very Indy-like adventure way. The lead character is a Bible Archeologist/Professor. He goes on adventures throughout the world looking for artifacts that proves the Bible to be true...but has to do it before the bad guys get there.