For worldwide do you mean?
There is Scott Classic Catalog which in a one volume book has countries of the world from 1840-1940 only. Also on Cds. Beware of CDs from Asia.
There is also buying Scott Standard 6 volumes used and a few years old for much cheaper.
There is buying only the pages of the country you are working on off of
ebay (cut out of a catalog) for a cheap price.
There is going to the library.
Depends on if you want to work on really new stamps or not. You could buy an older 1-2 volume Scottt for cheap, although in all of the above shipping is a consideration of course.
Buying older is good when you are just getting used to it all again and do not really have to have current up to date prices.