Ikea has some nice display cases in their catalogue,you can check out ebay,Craigslist,and ads for store display fixtures,or maybe stores going out of business.You can contract someone to build to your specs.Check antique stores for cabinets.
It all depends on how much space you have and how much you want to spend.
This subject has been dicussed,use the search feature,I remember many guys posting pics of their display setups and suggestions.