In short you only need an account here and editing your eqhost.ini file... And your set to play around...
But if you want to set up your own server, be it an eqemu server or localhost server etc, then you will need to download eqemu and mysql...
Of cause, you can download EQW to use if you like with any of the options.
Now, besides those there are other programs to help out, like the EQAdmin tool to help you on the database, its a nifty program that helps out, but you dont really *need* it.
The EQCollector or packet collector you dont need either - BUT!!!! If you have a live EQ account it can and will help out alot to use it while playing to help out collecting the data that EQEMU needs - making the EQEMU a better program for us all
Besides that I dunno really what else is out there of 3-party programs, but there are proberly more good ones for specific situations.