I don't have good references handy where I am right now, but Hotchips a couple of years ago had many examples, including a Memcache accelerator. A more down-to

I don't have good references handy where I am right now, but Hotchips a couple of years ago had many examples, including a Memcache accelerator. A more down-to-earth example shipped with an Arrow FPGA dev kit I got: they took a software and ported MPG123 (mp3 decoding). They then profiled it and isolated a candidate for acceleration (some moderately wide integer operation). The result saved meaningful amount of CPU cycles and power. (The FPGA board was battery driven, which is still unusual).