What are some of your favourites from the days before companies used to just give you a link to an online version to save themselves some cash? I used to love the little Command and Conquer ones that listed all the units and gave descriptions for them. IIRC, one of the Roller Coaster Tycoon ones had some neat history about the different rides. Sid Meier's Railroads! had a great one with lots of pictures of all the little train engines you could build, with the history of each, as well as some background on all the ambitious rail barons you could be.