Site audits:

Semrush
SEOSiteCheckup
SEOCentro
SEO Profiler
Moz Local
Open Site Explorer
Keyword Difficulty Checker
Mozbar Chrome Extension
SERPTrends SEO Extension
Stylish Chrome Extension
Beamusup
Structured Data Testing Tool

SEO browser

KW RESEARCH

KeywoordTool.io
KWfinder
LSI Graph
Google Keyword Planner

longtailpro.com

answerthepublic.com

ubersuggest.com

soovie.com

keywordshitter.com

spyfu.com

Search Engines

Google.com

Bing.com

Yahoo.com

UX Tools

fivessecondtest.com

usabilityhub.com

ONLINE SEO TOOLS

seobook.com

seoprofiler.com

CITATIONS

moz.com/local/search

whitespark.com

A great list of citation sites by category by Whitespark

semrush.com

Googlemybusiness.com

bingplacesforbusiness.com

infogroup.com

neustarlocaleze.com

acxiom.com

factual.com

foursquare.com

biz.yelp.com

ANALYTICS

Google Analytics
Google Search Console
Bing Search Console

LINK BUILDING

Email Hunter Chrome Extension
Pitchbox
Broken Link Checker Extension
Broken Link Check

REVIEW GENERATION
Grade.us
Pleper.com

CONTENT WRITERS
Writeraccess.com
Fiverr.com
Upwork.com
Onlinejobs.ph

WP PLUGINS FOR SEO

JSON-LD Schema Markup
Simple Site Maps
SEO Yoast

PAGE SPEED

Google Page Speed Insights
GTMETRIX

Google Mobile Friendly Site Test
Google Mobile Page Speed Test

EXTRAS

Copyscape

joinbytext.com

searchengineland.com

IMAGE Optimization
Compressor.io
Optimizilla.com
Imsanity.com