Below is a listing of Bible Student groups who adhere to the teachings of Charles Taze Russell in one form or another. It has been stated that the Society today has over 500 offshoots, that number may have grown since last I remember some ten years ago. The year next to the group is the year of its incorporation.
New Covenant Fellowship 1909 [Australia]
New Covenant Believers 1909
Associated Bible Students 1914 [Formerly IBSA, name changed in 1914]
Bible Students Publishing Company 1914 [UK]
Bible Fellowship Union 1917 [UK]
Angel of Jehovah Bible and Tract Society 1918 [F.L.A. Freytag]
Berean Bible Institute 1918 [Australia]
Stand Fast Bible Students Association 1918
Pastoral Bible Institute, Inc. 1918 [formed by the 4 ousted directors]
Laymen's Home Missionary Movement 1918 [Paul S.L. Johnson]
Forest Gate Church 1920 [UK]
Christian Truth Institute 1920? [UK]
New Jerusalem Fellowship 1922 [UK]
Elijah Voice Society 1923
Institute of Pyramidology 1923 [UK]
Servants of Yah 1925
Old Paths Publications 1925 [UK]
Christian Millennial Fellowship, Inc. 1928 [Gaetano Boccaccio]
Dawn Bible Students Association 1928 reorganized as DAWN in 1932
Watchers of the Morning 1937 [offshoot of Pastoral Bible Institute]
Goshen Fellowship 1951 [Jesse Hemery UK]
Epiphany Bible Students Association 1957 [John Hoefle]
Laodicean Home Missionary Movement 1957 [John Krewson]
These are the English speaking groups. There are foreign language groups all over Europe, the Middle East and Asia that publish their own journals and literature in cooperation with the USA groups.
The above are just the Bible Student groups, in the 1930s through the present, there have been Jehovah's Witness offshoots, too numerous to document.
Hope this helps.