Unlike most people here, I group by an 
overall "theme," rather than by series.  The 
reason for this is that I have very small 
collections for most shows (1 Cowboy Bebop, 1 
Mahou Tsukai Tai, 1 AnC, 2 Nightwalker, 3 Tylor, 
3 Inuyasha, and so on), and I can either have one 
big ugly Miscellaneous section, a ton of itty-
bitty galleries that don't seem worth the time it 
takes to load them, or several smaller, thematic 
galleries that are a lot more fun to put together 
^-^.  The only times I group by series are those 
that I have relatively many cels for, though I 
don't put up everything I have from those shows.  
I think it works pretty well.  

In my cel book, of course, everything is grouped 
by series.  I'm not mad >:D.