2006 may be a lower key touring year than 2005 was, as a lot of major acts were out in 2005.
For the U.S, in early 2006, here are some tours I know about:
The Rolling Stones from January-March and rumored to be returning in September,
The Strokes in March-April,
Franz Ferdinand in March-April or longer,
David Gilmour in selected cities in April,
INXS in January-February with another US tour leg planned for the Spring,
Coldplay in January-April,
The Pretenders in Southern California show in March,
Bon Jovi in January to at least March,
Oasis doing a few US dates in March,
Black Rebel Motorcycle Club through March,
Richard Ashcroft opening for Coldplay in March-April and maybe doing his own shows,
Aerosmith and Lenny Kravitz touring together into March,
Here's various other acts that may tour:
Pearl Jam should tour the US behind a new album,
The Who have indicated they will tour the US in 2006 with some new music released in one form or another,
Madonna rumored for this summer,
Paul McCartney is rumored for another US tour in the Spring,
Radiohead has indicated they will tour the US in the Summer,
Morrissey should be touring the US this summer,
Jet has a new album due in June so they should tour behind it,
The Offspring should tour behind their upcoming album,
Live has a new album out in April and should tour the US behind it,
The Red Hot Chili Peppers are planning to play the US off and on from July-December,
Don Henley and Stevie Nicks, may be touring together this summer,
Elvis Costello should be touring this year,
Tom Petty and the Heartbreakers intent to tour this year,
Bob Dylan should continue his touring,
Velvet Revolver are expected to have a new album this year and would tour behind it,
Bruce Springsteen and the E Street Band may have an album and tour later this year,
The Cure plan an album for this year, so a US tour could happen,
Sting is rumored to tour this year and has a date in Las Vegas at Tiger Woods charity show already announced for April 29th,
Travis will release a new album this year and should tour the US,
Eric Clapton may tour the US this year, as he already has shows in Europe,
a new version of The Cars is expected to tour this year,
Riders On The Storm, formerly The Doors of the 20th Century are expected to tour this year,
Simple Minds are expected to tour the US this year,
Sheryl Crow will probably tour more in the US this year,
Ray Davies is expected to tour the US,
The Pixies could do more touring this year,
John Lydon is expected to do a solo tour and possibly a Sex Pistols 30th anniversary tour.
There's a lot more that will happen, but those are some I have heard about.