Here are a list of links that you may find handy.
www.worldofspectrum.org – The place to be
Z80 Assembly for the ZX Spectrum Facebook Group – This site’s fb group
http://www.icemark.com/downloads/index.html – Sourcecode for ZX Spectrum Games
http://skoolkit.ca/ – Excellent site full of disassembled code
http://www.desdes.com/products/oldfiles/index.htm – Design Design games sources etc.
http://members.iinet.net.au/~msmcdoug/zx/knightlore_v100rc6.lst – Knight Lore source
http://www.users.globalnet.co.uk/~jg27paw4/pourri/rom-routines.txt – ROM routines list
https://web.archive.org/web/20150501015411/http://www.wearmouth.demon.co.uk/zx82.htm – ZX Spectrum ROM disassembly
http://chuntey.arjunnair.in/ – Lots of ZX Spectrum coding tutorials
http://clrhome.org/table/ – A nice table layout of the Z80 instruction set
