Here is an extensive list of memory addresses for various things in the Legend of Zelda Oracle of Ages. This is for Oracle of Ages [b]ONLY[/b]. Although OoA and OoS (Oracle of Seasons) are very similar the memory addresses are not in the exact same locations, nor are values the same. You can use these memory addresses in the VBA (Visual Boy Advance) Memory Viewer to edit various aspects of the game, or if you have knowledge on gameshark codes you could easily make them into gameshark codes for stuff such as permanent pegasus seed use.

[b]Table of Contents:[/b]
       - Life/Rupee Addresses
       - Item Addresses
               - Inventory Addresses
               - Item count
               - Weapon/Item Level
               - Miscellaneous Item Addresses
       - Ring Addresses
       - Animal Addresses
       - Miscellaneous Addresses
       - Credits

[b]Life/Rupee Addresses:[/b]

[u]Rupees:[/u]
C6AD - The first byte the game reads your rupee total from. Changes the ones and tens digits (0-99 rupees).
C6AE - Second byte, changes the hundreds digit (100+ rupees)

[u]Life:[/u]
C6AA - Your current life in-game
C6AB - Total amount of hearts you have

[b]Item Addresses:[/b]

[u]Inventory Addresses:[/u]
C688 - B Button
C689 - A button
C68A-C699 - Slots 1 to 16 on inventory screen.

[u]Item Count:[/u]
C6B9 - Number of ember seeds
C6BA - Number of scent seeds
C6BB - Number of pegasus seeds
C6BC - Number of gale seeds
C6BD - Number of mystery seeds
C6BE - Number of gasha seeds
C6B0 - Number of Bombs
C6AC - Number of pieces of heart

[u]Weapon/Item Level:[/u]
C6B2 - Sword Level
C6AF - Shield Level
C6B8 - Power Bracelet Level
C6B7 - Harp of Ages songs obtained

[u]Miscellaneous Item Addresses:[/u]
C6BF - Essences (FF = all essences)
C69F-C6A5 - Secondary Items (FF in all for all items with mermaid suit, or FF in all except C6A3 with FB for all items with flippers)
C69E - Seeds obtained for use (FF = all seeds)

[b]Ring Addresses:[/b]
C616-C61D - Rings obtained in ring list (FF for all rings in each list)
C6CC - Level of Ring Box
C6C6-C6CA - Rings in Ring Box
C6CB - Ring currently equipped
C6CD - Number of Rings (resets on inventory open)

[b]Animal Addresses:[/b]
C6B5 - Animal flute icon(01 Rickey, 02 Dimitri, 03 Moosh)
C610 - Animal Song+Animal+Map Features (0B Rickey, 0C Dimitri, 0D Moosh)

[b]Miscellaneous Addresses:[/b]
D00D = Links X position
D00B = Links Y position
CC2D = Active map group (00 present overworld, 01 past overworld, 02 present underwater, 03 past underwater, 04/05 dungeons, 06-07 side scrolling rooms)
CC2F = Map backup/real map to go into
CC30 = Active map
CC48 = Map to warp into

CE00-CEBF = Collision data (Same bit style as D033)
CF00-CFBF = Map data

Pegasus Seed timer = CC6C
Pegasus Seed timer loop = CC6D

D033 Bits:
00 - regular walking
C0 - touching up
0C - touching left
30 - touching down
03 - touching right
10 - top left corner (top end)
01 - top left corner (left side)
02 - bottom left corner (bottom end)
40 - bottom left corner (bottom end)
80 - bottom right corner (bottom end)
08 - bottom right corner (right side)
20 - top right corner (top end)
04 - top right corner (right side)

Note: Values can combine such as if you are touching both left side and top side, D033 will become CC
Note2: When pushing up against an object, D034 is set to 10.

[b]Credits:[/b]

Oracle of Ages Memory Address document written by Fatories. Special thanks to Lin for giving some memory addresses and helping with a few things. 

Other than a few memory addresses given by Lin, all were found using, the VBA memory viewer, by myself.