Go check
www.gundamofficial.com for the timeline.
Apparently there is one, and it's mainly separated in four diffrent eras.
U.C. / Universal Century - The original Gundam series, Zeta Gundam and all it's following sequels.
F.C. / Future Century - Only G Gundam takes place in this era, as far as I can tell.
A.C. / After Colony - Gundam Wing, Endless Waltz etc.
C.E. / Cosmic Era - Gundam SEED, Gundam SEED Destiny
Although there is a timeline, it's often treated much like the Final Fantasy series. That each new series is in a separate universe of sort, with no real references to the old Gundam series. That's because they usually change the whole development team every time. New writers, artists and directors.
By the way, check out Gundam SEED if you can find it. It's a great series.
And Gundam SEED Destiny is it's direct sequel.