How to disable "New Folder" command on the New menu in a List ?

If you are bugged with users creating "New Folder" in your list and if you want to disable the "New Folder" option then you can tweak the parameters in the List Element - "FolderCreation" to "NO" and that's it its all done. There are other parameters in the List which you can look for more Information.
http://msdn.microsoft.com/en-us/library/ms462947.aspx
AllowDeletion = "TRUE" "FALSE"
AllowEveryoneViewItems = "TRUE" "FALSE"
AlwaysIncludeContent = "TRUE" "FALSE"
BaseType = "0" "1" "2" "3" "4"
CacheSchema = "TRUE" "FALSE"
Catalog = "TRUE" "FALSE"
Category = "Libraries" "Communications" "Tracking" "Custom Lists" Default = "TRUE" "FALSE"
Description = "Text"
DisableAttachments = "TRUE" "FALSE"
DisallowContentTypes = "TRUE" "FALSE"
DisplayName = "Text"
DocumentTemplate = "Integer"
DontSaveInTemplate = "TRUE" "FALSE"
EditPage = "Text"
EnableModeration = "TRUE" "FALSE"
FeatureId = "Text"
FolderCreation = "TRUE" "FALSE"
Hidden = "TRUE" "FALSE"
HiddenList = "TRUE" "FALSE"
Image = "URL"
MustSaveRootFiles = "TRUE" "FALSE"
Name = "Text"
NewPage = "Text" NoCrawl = "TRUE" "FALSE"
OnQuickLaunch = "TRUE" "FALSE" Path = "Text"
RootWebOnly = "TRUE" "FALSE"
SecurityBits = "Text"
Sequence = "Integer" S
etupPath = "Text" SyncType = "Text" Type = "Integer" Unique = "TRUE" "FALSE" UseRootFolderForNavigation = "TRUE" "FALSE"
VersioningEnabled = "TRUE" "FALSE">
Also Check the Thread
http://social.msdn.microsoft.com/Forums/en-US/sharepointdevelopment/thread/af7abf69-2e68-427c-8880-273c5a722a1a