This is a basic 4 8-bit line RAM using RS latches.

Features:
Chose what line you want to clear (must be done before you write new information to a line)
Clear all lines
Read and Write can be done separately or at the same time
Ability to separately chose what line you read and write to/from with a 2 bit binary number

It is recommended that you select where your writing to before you select write.

Credit:
http://www.minecraftforum.net/forums/minecraft-discussion/redstone-discussion-and/337110-super-compact-vertical-decoder
for the 2 2-bit decoders i use to select what line for read/write

I have made a second post with a modified one of these that i will use for my own computer and may be better to use depending on what you're doing.
Second post:
www.planetminecraft.com/project/4-line-8-bit-ram-simpler/