You can view loads of Full Metal Alchemist manga here. The site displays the chapters in an online view, so you can view it right in your browser–no downloading. The site also has other nice features like anime, Full Metal news and character summaries.
You have to be 18 to view, but in the interest of listing everything I find in all genres, Akiba Angels has the hentai / doujin you want to see. Like other “similarly minded” sites, they display a lot pictures and several free samples, but you have to pay for more. There is a broad (no pun intended but enjoy it if you like) collection to choose from. Knock yourself out.