If you're not really swimming in the stuff, helmets and edged weapons are by far the most attractive 'mundane' uses. If you have more than your military needs, you can get fancy.
My favourites are socks and flasks. Each only takes one unit of processed adamantine, so you can make fancy socks for everyone! When looking at overall value from invested candy, flasks (and possibly crafts/goblets, but those have no practical value) are most efficient - three items with quality levels (a masterwork one should be worth 36 000) from a single wafer. Coins are a very poor choice, coins minted in your fort will always be of base quality - one wafer will give you one stack worth 3000. The only use of coins would be exploiting the melt returns bug.
When making furniture from the blue stuff, consider using the raw stone instead of the processed material. Raw adamantine works like any stone in masonry - one statue/hatch cover/mechanism/door or four blocks per boulder. Processed adamantine is 20% more valuable, but for this small increase in value it consumes 6-9 times the material and takes a lot of time to extract. Nine boulders can be turned into nine raw adamantine statues (each worth 75 000 if masterwork) or _one_ adamantine statue (a masterwork one would be worth 90 000).
Of course, if you're just looking for something to do with five hundred wafers you have left over after kitting out your military, ostentatious luxury is a very dwarven statement: build a well from admantine parts, switch all forges to adamantine anvils, pave a road with the stuff... on one obscenely bluemetal-rich embark, i built an archery pillbox from ~120 wafers.
Re: clothing - adamantine clothes are a luxury item, doubly so since they wear just like all other clothes. Making a bunch of socks makes a very clear statement, but you can also spice up your artefacts by keeping several bolts of blue cloth on hand - moody clothiers and weavers will use adamantine cloth as base material for their artefact if any is available (unless they have a preference for a specific other cloth type). Artefact adamantine clothes are obscenely valuable (and don't wear).