Harlan Coban has stand-alone thrillers, as well as a series with the repeating character, Myron Bolitar and his wonderfully-written psychotic friend, Win).
Lisa Gardner is terrific, as is Stuart Woods (the latter also has repeating characters, Stone Barrington, being one of them).
Robert Parker (Spenser for Hire) and Dennis Lehane (Shutter Island and Gone, Baby, Gone) are two more of my favorites, both Boston boys. Both have repeating characters. Lehane also has a great repeating psychotic character, Bubba.
Lawrence Sanders' "deadly sins" novels are excellent, too!
I love gift certificates to book stores! This past Christmas was the first one in years where I didn't get a Barnes & Nobles gift card. But I got a fantastic biography of Bonnie and Clyde that I'm eating up!
Lee