Im the GTA IV's internet, click the address bar and enter www.thingstheydonotwantyoutoknow.com. It looks like a mock hacker forum. They have maps there with flying rat loctions, car locations, vehicle locations, weapon loctions, health and armour loctions.
The only problem is for stuff like weapons and car locations is it doesn't tell you what car or what weapon. So you gotta go to them and find out which one it is.