Can anyone point me toward a thief themed adventure?  A clever heist?  Assassination?  Something cloak and dagger?

I was thinking about a casino location, perhaps a casino placed in an exotic location like an airship, or underwater.  I don't have anything concrete though and would love ideas.  

Keys to the Golden Vault is a compilation of heist adventures.  I can't speak to its quality because I stopped buying WotC books before it came out.

I personally like your idea about the casino in an airship.  You could have it be an Oceans 11 type heist, or you might take inspiration for one of the heists performed by Serenity's crew in the TV show, "Firefly", and you might even take elements of inspiration from Indiana Jones and the Last Crusade regarding Indiana and Henry Jones' misadventures in escaping from Germany on the Zeppelin.  You could even read the Artemis Fowl series, as the main character is repeatedly committing heists throughout the early books.

Draw on a lot of sources of information for inspiration, molding them together into something coherent, and you'll end up with something uniquely yours that your players should love.  Just don't get stuck on your idea of how things "should" go, because if there's one thing players are guaranteed to do, it's come up with ideas that the DM didn't, and we have to improvise.

I recently read somewhere, "The DM has the power to decide that the next adventure will be a heist, but the Players have the power to determine whether the theme music will be the Mission Impossible theme, or the Benny Hill theme."

Loke Battle Mats has a heist adventure that was free on RPG day.

Quote from FayetteGamer >>

Keys to the Golden Vault is a compilation of heist adventures.  I can't speak to its quality because I stopped buying WotC books before it came out.

I personally like your idea about the casino in an airship.  You could have it be an Oceans 11 type heist, or you might take inspiration for one of the heists performed by Serenity's crew in the TV show, "Firefly", and you might even take elements of inspiration from Indiana Jones and the Last Crusade regarding Indiana and Henry Jones' misadventures in escaping from Germany on the Zeppelin.  You could even read the Artemis Fowl series, as the main character is repeatedly committing heists throughout the early books.

Draw on a lot of sources of information for inspiration, molding them together into something coherent, and you'll end up with something uniquely yours that your players should love.  Just don't get stuck on your idea of how things "should" go, because if there's one thing players are guaranteed to do, it's come up with ideas that the DM didn't, and we have to improvise.

I recently read somewhere, "The DM has the power to decide that the next adventure will be a heist, but the Players have the power to determine whether the theme music will be the Mission Impossible theme, or the Benny Hill theme."

I never plan to far ahead nor do I have concrete plans for any adventure.  My players always do something I don't expect.  Most recently, exhume a body from a soldier's grave and smash the skull with a magical hammer, "just to make sure nothing happens?!?!?"  I definitely wasn't expecting that in a million years.  Still don't what they thought might happen.

Quote from JohnnyC1971 >>

Loke Battle Mats has a heist adventure that was free on RPG day.

 Unfortunately, this is no longer available 

I found something pretty fun.  The Star of Olindor.  The idea is that a local merchant has procured a magical item that cures disease.  He therefore starts a plague, and makes a fortune selling the cure.  The goal is to uncover the plot and then steal the gem from the merchant, giving it to a lawful good cleric of healing.  

I modified it quite a bit but I really like the gist and it drops well into my one-shot town, Riverfast.  

I had a lot of fun with the disease as well.....

As the name suggest Hell's Lung attacks the victim’s lungs, causing hypoxia, shortness of brath and ultimately alveolar necrosis and hemoptysis. The spores are inhaled and the disease normally has a one-day incubation period.  Inhaling a large dose (LD99) results in death in a few hours unless save vs poison at -10 is made.  Symptoms begin with malaise, fever, and cough.  Failing a 2nd poison save results in 1d3 constitution loss (permanent unless healed by the Star). After 1d6 days save vs poison again.  If the person fails, hemoptysis begins and is uniformly fatal in 1d3 days.  The fomites are not infective so caring for the sick is not necessarily a dangerous activity.

I figured as much, however someone may be parting with their copy if they're interested. At least it's an option, right?