Restriction endonucleases can be considered as the set of "working horses" aimed to point out specific sequences, to produce "sticky ends", to provide DNA fragment isolation and cloning. In spite of the successful replacement of restriction endonucleases by PCR-techniques in some applications, these enzymes still have rather high potential for DNA manipulations. A lot of procedures like mutation assays, mapping and cloning can hardly survive without restriction endonucleases even today.
The list of restriction endonucleases is comprehensive, but still not complete nowadays. There are more than 800 isoschizomers and more than 300 specificities, all of them are perfectly compiled in REBASE http://rebase.neb.com/rebase/rebase.html by New England Biolabs.
As a matter of fact a bit more than 40 specificities are really requested in everyday work in the majority of laboratories. All of them and more are listed here.