Look for coins that radically differ from Bitcoin. Unique features will be increasingly important, as both new and old coins become lost in a sea of clones.
eMunie, NXT, MSC, and Ripple stand out.
eMunie, by design, may be a poor choice for speculation; it is designed for stability.
NXT and MSC are young, and there is question over possible fundamental design flaws.
Ripple offers the most mature platform, backed by a well funded company, and brings to the table many great features: ability to handle any currency, internal exchange, and fast transactions. What is already there is great, and the future looks even brighter:
https://ripple.com/wiki/ContractsRipple is designed at a core level for external currencies. Even Bitcoin and alts can be used through it to make instant payments or exchange.
XRP is the internal currency that the system uses to make it all possible---and the investment opportunity.
Source code here:
https://github.com/ripple