Block managers...the one I got is called "CADLIBDU" forgot where I got it though its not the best but I didnt have to buy it. I use it on a network but it is touchy, I have to add the blocks in manually in text file. FOr some reason it doesnt do it automatically over a network. If it is on your local CPU it works great.
Look for LISP files these are always a big help. Script Files too. If you use scripts to print or somethig that will be done to multiple drawings go to AUTODESK and download the SCRIPTPRO program, its free and works really well.