I have a set of scripts that will generate ebuilds for pretty much any coin with a GitHub repo. It's in my Portage overlay:
https://github.com/salfter/portage (look under net-p2p)
This overlay already has ebuilds for a bunch of different coins, most of which were generated by these scripts:
42 (as "coin42")
acoin
anoncoin
bitgem
digibyte
dogecoin
earthcoin
einsteinium
emark
fastcoin
fireflycoin
fluttercoin
fudcoin
grandcoin
joulecoin
nautiluscoin
netcoin
novacoin
opensourcecoin
ppcoin
primecoin
sexcoin
spots2
tekcoin
terracoin
titcoin
unobtanium
viacoin
yacoin
zetacoin
If your favorite coin isn't in there, you can probably get it up and syncing to the blockchain in a few minutes. See
https://salfter.github.io/ to get started.