VBSpeed

The Visual Basic Performance Site - focus on VB6 but transferrable across to VBA.

Access Ribbon

An excellent resource for information for developing custom ribbon XML. Although principally targeted at Access, it is equally applicable to Excel, Word and PowerPoint.

Ron de Bruin - Ribbons/QAT

A leading resource for information/samples on developing custom ribbons and context menus. (Hosted on Jan Karel Pieterse's site)

Office MSO Icons

Ribbon icons can often use one of the 1500 (3 pages on this site) MSO icons wich pre-exist in Office applications.

RubberDuck's style guide

Has some great intermediate - advanced guidance.

VB6 Coding conventions

Variable/Class/Module naming conventions used in VBA. Greatly helps organisation in VBE (unless you have rubberduck).

Thunder - The birth of Visual Basic

A little article about the birth of VB7/VBA.

My First Bill Gates Review

Joel Spolsky, program manager for the Excel team, recounts his first Bill Gates review. Joel got numerous features added e.g. IDispatch, Variant, For each and With. It also discusses the dreaded Date bug ported to Excel from Lotus 123.

Ruby, EB and DLL composition

Translated copy of VBStreets article created by Russian VBer Хакер. Details the composition of the VB6 and VBA dlls in amongst the history of the language.

PCode Internals

VBA is compiled to PCode. Understanding the lower level P-Code is a topic of heavy interest and research.

How many lines of code in EB

Untranlated article by Russian VBer Хакер which estimates the number of lines of code in VB6/VBA.

SAFEARRAYS

The internal structure of arrays.

Articles by Sancarn

Various articles written by Sancarn about VBA including, performance, actual issues with VBA etc.

JKP API Declarations

Microsoft Office Code Compatibility Inspector

The Microsoft Office Code Compatibility Inspector was designed by Microsoft to troubleshoot compatibility issues with VBA code as when upgrading Office from 32-bit to 64-bit. MS has not maintained a link to the software for download from its servers, though versions of it are apparently available…

Planet Source Code

A code repository GitHub which holds copious amounts of code. The site was closed down in 2023, but fortunately all VBA/VB6 samples were archived on GitHub today. Possibly not the entire collection (?) of projects/source code that was previously available at the PSC website.

vbAccelerator Archive

Archived copy of vbAccelerator site (articles, source code, etc.) that disappeared in 2015, reappeared in 2018, and anyone's guess what's going to next… Primarily VB6, but useful VBA resource.

Excel Development Platform Blog

Blog dealing with advanced topics/VBA.

MSDN VBA Documentation

MS-VBAL Language Spec

Ron de Bruin

Simple-Intermediate topics. Note: Ron has archived all these sites, it will not be updated, and some information is out of date, yet it is still an incredible resource for VBA.

Bytecomb VBA Reference

Intermediate-advanced topics.

Chip Pearson's website

Great resource for beginners-intermediate.

VBA for smarties

A great reference to numerous data structures and mechanics.

Rubberduck Blog

Intermediate-Advanced topics.

MS KB Archive

Massive archive of vb6/vba problems, solutions and tutorials.

Articles by Sancarn

Various articles written by Sancarn about VBA including, performance, actual issues with VBA etc.

The VBA Help

A site dedicated to VBA with a large number of instructive blog posts. Written by the author of VBE_Extras, an AddIn for the VBA IDE and VBE_Colours, a small utility to configure the available colors used by the VBA IDE.

Hard Core Visual Basic

An advanced programmer's guide to the new 5.0 version of Visual Basic. Includes a core set of utilities, shortcuts, and solutions to problems to achieve a wide range of functional programs. A hard book also exists. Also check out the Comments and corrections.

The VBA Developer's Handbook

Write bulletproof VBA code for any situation. This book is the essential resource for developers working with any of the more than 300 products that employ the "Visual Basic for Applications" programming language. Hardbacks also available elsewhere.

Advanced Visual Basic 6

Power Techniques for Everyday Programs Matthew Curland. Hardbacks also available elsewhere.

Professional Excel Development

In this book, four world-class Microsoft® Excel developers offer start-to-finish guidance for building powerful, robust, and secure applications with Excel. Hardbacks also available.

(E-Book) VBA beginners

(E-Book) Excel VBA beginners

Excel Macro Mastery

Paul Kelly (MVP) - excelmacromastery.com.

Sigma Coding

Large catalogue of tutorials - beginner through to advanced. Delves into interesting areas of VBA not explored by other content creators.

WiseOwl's VBA tutorials

Great all-round resource for VBA. Perfect introduction for beginners. In-depth lessons into all aspects of VBA. Huge playlist that covers most types of VBA.

Excel VBA Is Fun

Excel for Freelancers

Hands-on tutorials to developing specific applications from beginning through to end. All levels.

Leila Gharani

Office-wide focus - useful for beginners.

Reddit

Daily VBA Q&A. Occasional Pro-Tip sharing and Show & Tell library publishing.

Stack Overflow

A great place to ask questions. Duplicate questions are flagged as duplicates and send the author to the correct place.

Chandoo

Forum for the Chandoo - the blog of Purna Duggirala (MVP). Very active.

Visual Basic Discord

A chat room for VB.NET/VBA/VB6 fanatics.

Excel Discord

Discord server moderated by Tim Heng (Excel MVP) with focus on helping Excel users.

MrExcel

Mostly Excel generic, but a lot of VBA content can be found here also.

Excel Forum

VBForums - Office Development

Forum with focus on VB6/.NET with VBA section.