I use a simple batch file to copy all my referenced packages to a shared folder.
--- syncnuget.bat ---
for /f "usebackq tokens=*" %%n in (`dir /b /s packages\*.nupkg`) do copy "%%n" C:\Path\To\Repository /y
Just run this batch file from your solution root.
It's always a good idea to have a local copy of all your packages since as we've recently seen, there are times when NuGet goes down which could impact development or continuous builds.