If they are pkg files that you have downloaded from somewhere, they are probably in your download folder (or a folder of your choice) and can be deleted without any problem.
However, if they are in HD > Library > Receipts, then leave them alone. Deleting these will result in a whole lot of hassle the next time you run software update.
This is the folder that Software update checks to see what you have on your machine. Removing the receipts for updates and patches will cause the system to believe that you do not have them and download the software again.
When you run Repair Permissions, this is the folder that is used to check what the permissions should be.
Bottom line, only delete .pkg files that you have downloaded.
Hope this helps
I have been cleaning up my hard drive and I noticed that there is over a gigabyte of .pkg files for various updates in the packages folder.
Is it worth backing these up before deleting them? I figure that if I needed to re-install I would just get the latest security and application updates.
What do you think?