It depends on where you are going exactly, but either:
North Lake Tahoe Express
or any taxi service in the Reno, Truckee, North or South Lake Tahoe area. There should be a line up of cabs outside of baggage claim. Unfortunately (in my experience), the options are limited.
Tahoe Riverfront Realty, Inc.
DRE# 01494444... more
There is a water taxi service planned between South Lake Tahoe at Zephyr Cove to the Homewood Ski area, starting in 2012. If you are still interested, send me an email and I'll forward the info.
BHG Mason McDuffie