Tennis:
Tennis Australia
WTA tour home page
WTA results (simple text only page with extensive info on the wta tour results)
Alicias' statistics (another good text only site)
Australian Open
US Open
Wimbledon
French Open
Other Tournaments:
Toray Pan Pacific Open (29 Jan - 3 Feb)
Qatar Totalfinaelf Open (11 Feb - 18 Feb)
Nasdaq 100 Open (20 March - 31 March)
Sarasota Open (1 April - 7 April)
Bausch & Lomb Championships (8 April - 14 April)
Family Circle Cup (13 April - 21 April)
Eastbourne (17 June - 24 June)

Other Sites:
Fox Sports very useful Australian sports resource