The largest and most comprehensive NFL mod for Madden NFL 08 is the Football-Freaks/FootballIdiot Mod, which can be found here. It updates uniforms, rosters, stadiums, and more to the current season.
Updated uniforms and rosters are available on the FootballIdiot Forums.
Additionally, multiple college football mods can also be found at FootballIdiot.
The original start screen features the cover feature athlete, Vince Young, in his Tennessee Titans uniform. He subsequently played for the Philadelphia Eagles. An updated set of start screens with choices for each team is available on the FootballIdiot Forums.
EA has shut down the multiplayer matchup servers. However, there are workarounds, including entering the other player's IP address manually or using a VPN. There are active leagues, including this one.
"Synchronization Error" can occur if both players have added any mods or additional folders that do not coincide with each other. Rosters, Saved players, and other items that are saved by the player in the game do not count as issues.
The program has compatibility issues with Windows 8. When attempting to start the program, intermittently a message will pop up stating "This application is not compatible with the installed operating system. Please upgrade to Windows 98SE, Windows 2000 or better." and the program will not start. Using compatibility mode for Windows 7, XP SP3, or Vista does not solve the problem.
Currently there is no fix.