This feels like it has a vague danger of turning into one of those 
eternal "definition of power pop" threads, but what the heck.  Top 15, 
in alphabetical order:

The Beatifics
Allen Clapp/The Orange Peels
Cotton Mather
Jason Falkner
The Fastbacks
Fountains of Wayne
The Greenberry Woods/Splitsville
The Hang Ups
The Lucky Bishops
The Minders
The Posies
The Sneetches
The Summer Suns and their various related bands
The Trolleyvox
Zumpano/The New Pornographers/Sparrow

Five artists whose best work was done before, say, 1991, but were 
still active:
Marshall Crenshaw
Tommy Keene
The Pursuit of Happiness
Redd Kross
The Smithereens

S