Twitter is being used a lot lately to engage customers with brands, one the most effective ways I’ve seen it being used is for hosting treasure hunts.

This method seems to be an excellent way for brands that are just starting out in social media. It allows them to test the waters to see how their customers will react and most importantly how they feel about getting out from behind the one-way broadcast messaging of the past and engage with their customers in a two-way conversation.

They can also be a lot of fun, for those running them and those who choose to be a part of them.

Here are some of the best ones I’ve seen in action…

Tony Hawk’s Hidden Skateboards

Tony Hawk was the raddest skater when I was a kid (and we weren’t being ironic when we were using that word), and he’s still going at it today. He and his crew hid about sixty skateboards all over the world, sending out clues via Twitter to help his fans find them. (@TonyHawk)

Levis: iSpyLevis

This campaign started around Sydney, eventually expanding to other capital cities such as Melbourne, Brisbane and Perth – even crossing the ditch to New Zealand. The iSpyLevis crew encourage people to come out and find them and to ask “Are they Levi’s?” to complete strangers in denim in the hope of finding the person behind the @iSpyLevi and a free pair of Levis. (@IspyLevis)

BMW & Need For Speed:Shift

This one was a clever twist on the usual. As part of the launch of the Need For Speed:Shift game, gamers and BMW lovers were asked to try and find a BMW in Google Street View, then send a tweet with a screenshot of it with the hashtag #NFS to @NeedForSpeed. The part that I liked the most about this one is that by getting contestants to send their tweet to @NeedForSpeed, it generated content in a hashtag and buzz on Twitter without the contestants spamming their followers (@replies are only seen by those who follow the same people). (@NeedForSpeed)

Eminem

Slim Shady might not follow anyone on Twitter, but he gives 300,000+ people a reason to follow him as he (or more likely his entourage) sneak around hiding tickets to his concerts and tweeting their locations. Restaurants, music store, clothing stores, bars, public monuments even seemingly random people on the street are good places to hide tickets its seems. (@Eminem)

Borders & Dan Brown: “The Last Symbol”

Borders hosted a treasure hunt for fans of Dan Brown to promote the release of his book “The Lost Symbol”. Taking a leaf out of the classic “Charlie and the Chocolate Factory”, by hiding 80 golden tickets in 80 US stores, to gave away free copies of “The Lost Symbol” signed by the author to anyone who found a ticket. Clues to the where the tickets were could be found were sent out by Borders on Twitter. (@BordersMedia)

Lily Allen

Lily’s treasure hunts are similar to Eminem’s, although Lily appears to be hiding the tickets herself rather than getting someone else to do it for her. She is far more conversational with her fans and has far more followers too. Given that a good part of her success was due to her gaining a following on MySpace before scoring a recording contract, Allen is no stranger to using social media to her advantage. (@LilyroseAllen)