Leonard Slatkin is currently the National Symphony Orchestra Music Director
During his 7-season tenure in this position, the orchestra has performed many highly-praised european, asian, and domestic tours. Leo also has the NSO doing a national radio series, to better expose the public to great classical works.
Leonard Slatkin has appeared in the past with many important international Orchestras. Among others, the New York Philharmonic, the Berlin Philharmonic (which is often featured on the Deutsche Grammophon label, my personal favourite due to its high production quality and excellend direction), the Cleveland Orchestra (which I have never experienced but am assured is worthy of respect, under Christoph von Dohnanyi), and the Metropolitan Opera.
Slatkin is also currently the chief conductor of the BBC Symphony Orchestra and is a conductor laureate of the Saint Louis Symphony, on the heels of his 17 year directorship there. Ouroboros kidly reminds me that Slatkin's time at the Saint Louis is very noteworthy - he took an unremarkable, backwater orchestra and turned it into v ital, skilled and respected group of performers. He was first associated with them in 1968, and became their music director in 1979. For the great changes he effected there, he earned much critical acclaim. It was at the close of this orchestra's 1996 seaons that he became conductor laureate.
Slatkin is notable for his commitment to american music, and creative programming, in addition to high-quality performances and recordings.
From what I can tell by looking at his picture, he's not anyting like the "maestro" of Seinfeld fame.