In 2012, AMD released their Piledriver architecture, which is what is in all currently-for-sale AMD socket AM3+ CPUs (4, 6 and 8 core, 32nm).
In 2013, AMD released a refresh to Piledriver called Steamroller, which is what is in their current FM2+ APUs (4 cores only, 28nm).
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Steamroller and Piledriver have significantly worse performance-per-core than Intel's current lineup, but AMD will sell you far more cores at the same price.
Piledriver (AM3+, 32nm) has slowly been reduced in price as Intel has released new CPUs, but has not been refreshed. The FX-8 series were originally released against Intel's i7's, but lately are priced near and more often compared with Intel's i3 CPUs. The performance is good for what you pay, but they are power-hungry and use a very, very old socket.
Steamroller (FM2+, 28nm) competes fairly well in the low-end market, providing near-i3 performance in most CPU related tasks, with a much faster iGPU, at around the same or lower price. The platform is modern too. Steamroller has slightly better performance-per-clock than Piledriver, but does not come in 6 or 8 core variants.
EDIT: Excavator is a 2015 refresh for FM2+, still 28nm, but I haven't heard too terribly much about it. I don't think much (anything?) is changed over Steamroller in terms of performance, but power consumption is much better, and it competes better with Intel's mobile lineup.