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

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

Acting on items

s        : star item
t        : tag item
e        : email item
<Shift> + s    : share item
<Shift> + d    : share item with note
v        : view original
o/enter        : expand/collapse item (list only)
c        : add comment
<Shift> + c    : view comments
m        : mark item as read/unread
<Shift> + 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 <Shift> + s: go to shared items
g then u    : open subscription selector
g then t    : open tag selector
g then <Shift> + t: go to trends page
g then d    : go to discovery page
g then f    : open friend selector
g then <Shift> + 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