1. Beyond the Highland Mist (1999) 2. To Tame a Highland Warrior (1999) 3. The Highlander's Touch (2000) 4. Kiss of the Highlander (2001) 5. The Dark Highlander (2002) 6. The Immortal Highlander (2004) 7. Spell of the Highlander (2005)
I got this from another website, but I believe it's correct.
They can stand alone, but it's always better to read them in order. There is one repeating character, but I think he's only in three. He is in the first and third one as a secondary character, and then his book is The Immortal Highlander (his name is Adam), so I would suggest not reading that one before the other two. But other than that it's no big deal what order you read them in.