I used to hate running, but I got hooked back in 2008 with my first 10K "race," the Nike+ Human Race. On race day, it didn't matter where you were, you could run and log your 10K race with Nike+. I was traveling in Argentina, so I ran mine in the polo fields of El Colibri in Cordoba, Argentina (extremely windy). I ran my first half-marathon in Sydney last May (perfect weather), and I just signed up for my first marathon in Stockholm next July (fingers crossed). It is the 100th anniversary of the 1912 Olympic marathon and it will follow the same course.
Running is a great way to see a place. Whenever I travel now, I look for nice running routes -- Stanley Park in Vancouver and Central Park in New York are two of my favorite 10K runs. For me, mixing travel with running is a great training motivator. So as a way to kick-start my marathon training after a knee injury, I decided to come up with my list of dream race destinations. Many of the marathons also offer shorter distance races such as half-marathons and 10Ks.
For now though, my sights are fixed firmly on Stockholm.
Albatros Travel organizes a series of adventure marathons which are run on rough terrain such as its upcoming Petra Marathon. Amazing Running Tours, Global Running Tours and Marathon Guide are great resources for race information and travel planning.
When the 42K marathon is no longer challenging, there's a whole other world of ultra marathons, 100-250K races such as Racing the Planet's Gobi March.