MAJOR:
-BTC Bitcoin - first, strongest, most accepted, most mined, high volume market, stable value, a true currency
-LTC Litecoin - second only to BTC , faster than BTC, Small efficiency gap between GPUs and CPUs , ASIC - proof
-NMC Namecoin merged mined with BTC, used for alternative p2p domain system
MINOR:
-PPC PPcoin Proof Of Stake [very innovative, low energy ] , compatibile with BTC miners
-TRC Terracoin based on BTC, fast difficulty adjustment - miner-jump resonance resistant
-DVC Devcoin merged mined with BTC, 90% of generation goes to foundation, 10% to miners
-IXC IxCoin merged mined with BTC, premined 580k coins but still alive
-NVC NovaCoin - scrypt hashing[like LTC] , proof of stake [like PPC] , controversial
-FRC Freicoin back alive. 4.89% anual demurrage. for the first 3 years 80% block subsidy goes to foundation, 20% to miners
NEW:
-Bytecoin- the 1:1 bitcoin copycat. really bad difficulty adjustment for altcoin, extremally high hashrate for that young coin.
DEAD / DYING :
-LQC Liquidcoin made to be very fast at constant difficulty, dead [pool closed, exchange closed]
-SC Solidcoin - dying (10-20% fee), designed to improove IxCoin, hard to be neutral on this one, 1.0 was a premine scam, 2.0 says BTC is pyramid scheme.
-GG Geist Geld experiment on BTC algorithm, how fast can it go? just for sience.
-TBX Tenebrix great idea of cpu-friendly mining with scrypt, but premined with 7.7milion coins - alive but little support due to premining
-FBX Fairbrix - Tenebrix without the premine, bad launch, alive but little support.
-I0C I0coin - ixcoin without the premine. Dead
-CLC Coiledcoin - some nice ideas, but killed in 51% attack
-RUC Rucoin - copy of bitcoin, only difference is that is developed in russian not english. reborn much different, not confirmed if it is the same blockchain, both scrypt[like LTC] and sha256d , nice client !warning! not opensource !
-TimeKoin - PHP webbased coin, alive but not used or traded.
-Beertokens -abitious [impossible?] try to stabilize price against commodity.
-BBQ BBQCoin - killed in 51% attack on launch, now revived and
-MMM MMMcoin - Dead coin by notorious scamer SPMavrodi, named "yes we can" "my mozem mnogoye"
NOT A COIN / NEVER FULLY LAUNCHED:
-DigiCash - historical try for digital curency by David Chaum, failed.
http://en.wikipedia.org/wiki/DigiCash
e-cash and e-money are part of / continuation of digicash . Possibly where Bitcoin came from.
Ripples (XRP) -
http://ripple.com , no mining - all coins available at start 80% foundation, and 20% develeopers. centralized, not opensource. not designed to be a currency, but an IOU exchange.
Amazon Coin - centralized private scrip launched by Amazon and pegged to USD, not cryptographic at all, just a name.
WEEDS never realy active and now dead -
https://bitcointalk.org/index.php?topic=24209.msg300830#msg300830
Groupcoin - still alive but never realy active
https://bitcointalk.org/index.php?topic=24813.0
Opencoin - opensource version of digicash, opencoin.org , not launched yet
RealPay 100% coins at start, centralized, never realy launched ,site is dead
https://bitcointalk.org/index.php?all=;topic=62565.0
-Qubic - coins are produced at the rate determined by quorum of miners, not set by developers. Never launched.