Ascending Pea Pattern generator
APL, 32 characters
⍪⌽({⍵,⍨,/{⌽⍵,+/⍵⍷d}¨⍳⌈/d←⊃⍵}⍣⎕)1

This generates lines starting from 0 (i.e. 0 generates 1, 1 generates 1 followed by 1 1, etc.), as specified by user input. I used Dyalog APL for this, and ⎕IO should be set to its default of 1.
Example:
      ⍪⌽({⍵,⍨,/{⌽⍵,+/⍵⍷d}¨⍳⌈/d←⊃⍵}⍣⎕)1
⎕:
      0
1

      ⍪⌽({⍵,⍨,/{⌽⍵,+/⍵⍷d}¨⍳⌈/d←⊃⍵}⍣⎕)1
⎕:
      13
               1 
             1 1 
             2 1 
         1 1 1 2 
         3 1 1 2 
     2 1 1 2 1 3 
     3 1 2 2 1 3 
     2 1 2 2 2 3 
     1 1 4 2 1 3 
 3 1 1 2 1 3 1 4 
 4 1 1 2 2 3 1 4 
 3 1 2 2 1 3 2 4 
 2 1 3 2 2 3 1 4 
 2 1 3 2 2 3 1 4

Once I get some more time, I'll write up an explanation. ⍨