The House of Commons Library has produced an excellent Standard Note on Statutory Instruments - which anyone who wants to know about law & laws - should read.
It is available at http://www.parliament.uk/briefing-papers/SN06509.pdf
If you want to know which Statutory Instruments have been laid before Parliament at any point in time visit http://www.publications.parliament.uk/pa/cm/cmsilist/cmsilist.htm (a PDF version can be accessed here)
Reports published by the Joint Committee on Statutory Instruments can be downloaded from http://www.parliament.uk/business/committees/committees-a-z/joint-select/statutory-instruments/
[This committee deals with the issues of the legality (whether they are outside the power granted - 'ultra vires') of draft SIs and whether there are concerns about defective drafting]
Reports published by the House of Lords Merits of Statutory Instruments can be downloaded from
http://www.parliament.uk/business/committees/committees-a-z/lords-select/secondary-legislation-scrutiny-committee/publications/previous-sessions/session-2012-13/
[This committee - as the name suggests - is about the merits of the particular provisions]
Statutory Instruments passed since 1987 can be accessed at http://www.legislation.gov.uk/uksi