This page contains information about the secret stashes that can be found in S.T.A.L.K.E.R.: Shadow of Chernobyl. To find items in (and the locations of) secret stashes you first need to find information about the stash. This information can be found on dead humans, ie. stalkers, bandits, army personnel, and even some zombified stalkers. If you find information about a stash, the PDA icon will start to flash. The title and description of each stash is taken from the message you get when hovering the mouse cursor over the stash in the map of the PDA.
When you have found enough information about a stash it will be shown on your map - both the map in the PDA and in the minimap (if you're close enough). Once you find and loot a stash the icon will disappear. You can find information about the same stash several times - if you do, the contents of the stash will be multiplied by the number of times you've found the information; say, for example, you've found a stash with a medkit and 5 bandages in it. If you have found information about that stash three times, the actual content will be 3 medkits and 15 bandages. If you have found information about a stash more than once, without looting it in the meantime, the icon will not disappar from the map once you do pick up the items - I reckon this is a bug. You can remove the icon yourself by putting something into the stash and then taking it again; this should clear the stash marker off your map.