https://bitcointalk.org/?topic=205878

This encoding is designed so that it could replace Base58Check in new data, 
with the following goals in mind:
- Impossible(?) to manipulate without completely changing it
- Clearly identifiable prefix, regardless of data size
- Cheaper to process (simpler and faster code; it's a power-of-two radix)
- Fixed length string for fixed length data
- More unambiguous (removal of chars 'isuvzSVZ')
- Compatible with using seven-segment displays
- Altcoin friendly (16 bit namespace, which can be read without decoding)

Since there are fewer digits and more identifying/signature characters, 
addresses are longer. This should be less of a problem since ordinary users 
will hopefully be using addresses less common as the payment protocol becomes 
more popular.

Example Python code (including tests) is attached.
I can write up a formal BIP if this seems useful.

For example:

160 bits of data, such as current addresses:
    2nc111dhAPE2aUdYAOF88JhLn5jEjbULy4eFe9tyFYFE8
An ordinary P2SH destination, incorporating Greg's "require the hash mid-image 
to be relayed" concept (256 bits of data):
    2bc511A95e74P13dPb6b5t7yrh12EhC363ayH98n1cFbr3rAHdA49nCcC1G3P71j
The same key in Namecoin:
    2nc5119ttL35HPhc3Hh6aHe2tOhF6rdFtAOE1ahFLt9Ecabhcn5FLea5Le71P56C
The example "puzzle" script from the wiki (arbitrary scripting):
    2bc311d126acCyAnHAjabeUtOHcr7F811j4UYE6ECtOcbcGGn4O9chAt7O7y2LU9ty9cnG4
An alternative for BIP32 extended public keys (560 bits):
    2bc911AcchHheAGFnn9LC6FdF7bOc99APJtcEc46U655JheH6LCr3Y333eFEOtPJ9rj22rEcchHheAGFnn9LC6FdF7bOc99APJtcEc46U655JheH6LCr3YJCtPYea
An alternative for BIP32 extended private keys (552 bits):
    2bcb11O77GHdP53FH7Jh44OdEh3rLd4eFr2h7c8rGeErELG18yCy9O7L9LednyHJa5hyeAP77GHdP53FH7Jh44OdEh3rLd4eFr2h7c8rGeErELG18yCyGG5drPF1