Where can I find...
 

...the list of codes for summoning stuff in-game? Someone said that it was on the website, but I am unable to find it.

noob
 

/help for EQ commands
#help for EQEmu commands
#itemsearch (name) -if applicable
#summonitem (itemnummber from itemsearch) -if applicable

Just ask in-game if you need to know something else.

the readme has all the commands and tells you what each does.

As for codes for summoning as in what things you can summon, that's just items that you could find on eq websites.