I do not know of the existence of a good manual, but one of the ways I used to be updated is read new commands in the user manual.

Look at this website:

http://www.esri.pl/szkolenia/centrum-ksztalcenia-e-gis

http://www.geo.uni.lodz.pl/news/1449/15/Szkolenia-z-ArcGIS

And the results of the exercise ?? You can always go to 217K on Kopcińskiego street, we will help :)

for ArcGIS 9.3

http://webhelp.esri.com/ARCGISDESKTOP/9.3/tutorials/tutorials.htm

for  ARCGIS 10

http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00v20000000t000000.htm