By default, in Finder folders are shown in between all other files. alphabetically. There was a hint for Snow Leopard that showed how to show folders first in Finder, which is not working on Lion. This is because of the file:
/System/Library/CoreServices/Finder.app/Contents/Resources/English.lproj/InfoPlist.strings
sudo plutil -convert xml1 /System/Library/CoreServices/Finder.app/Contents/Resources/English.lproj/InfoPlist.strings
sudo vi /System/Library/CoreServices/Finder.app/Contents/Resources/English.lproj/InfoPlist.strings
[raw2] <key>Folder</key> [/raw2] [raw2] <string>Folder</string> [/raw2]
[raw2] <key>Folder</key> [/raw2] [raw2] <string> Folder</string> [/raw2]
sudo plutil -convert binary1 /System/Library/CoreServices/Finder.app/Contents/Resources/English.lproj/InfoPlist.string
Mac OS X Hints
http://hints.macworld.com/article.php?story=2011072120153685