Google Reader has lots of useful keyboard shortcuts. Here is the list.

Navigation
j/k : next/previous item
space : next item or page
+ space : previous item or page
+ n/p : next/previous subscription
n/p : item scan down/up (list only)
+ x : expand folder
v: view original
+ o : open subscription or folder


Acting on items

s : star item
t : tag item
e : email item
+ s : share item
+ d : share item with note
v : view original
o/enter : expand/collapse item (list only)
c : add comment
+ c : view comments
m : mark item as read/unread
+ a : mark all as read

Jumping

g then h : go home
g then a : go to all items
g then s : go to starred items
g then + s: go to shared items
g then u : open subscription selector
g then t : open tag selector
g then + t: go to trends page
g then d : go to discovery page
g then f : open friend selector
g then + f: go to friends’ shared items
g then c : go to comment view

Application

r : refresh
u : toggle full screen mode
1 : switch to expanded view
2 : switch to list view
/ : move cursor to search box
a : add a subscription
= : increase magnification
- : decrease magnification
via: Google Reader