Elementary elements

Alphabet

Spelling of names and surnames
Green route (level 1): The English alphabet
Red route (level 2): Alphabet - spelling 
Orange (level 3): Alphabetical order

Adjectives

Level 1: Adjectives exercises 
Level 2: Order of adjectives
Level 3: -ed or -ing in adjectives

Adjectives opposites
Green route: Opposites exercises. Adjectives, nouns and verbs
Red route:  Opposites - antonyms - exercises

Auxiliaries

Can & could, may & might, ought to, have to, must, be able to, to be allowed, shall & should.  
Can or could Can and could - modal verbs exercises 
Auxiliaries Verb tenses 2: exercises

Videos 
Auxiliary Verbs (Helping Verbs) | Learn English
Types of Modal Verbs

Comparisons

Comparitive 1 Comparatives exercises

Comparitive 2 Comparative and superlative

Comparitive 3 As...as / like / more

Conditionals

What if clauses ... 
Zero conditional: Zero conditional exercises
First conditional: First conditional exercises - if clauses
Second conditional: Second conditional exercises
Third conditional: Third conditional exercises - Conditional sentences type III
Mixed conditional: Mixed conditional exercises - intermediate level

Definite and indefinite articles

A - an - the 

Practice with definite and indefinite articles: Articles exercises: a, an - English grammar

Definite and indefinite articles: Articles: definite / indefinite exercises 

The definite article THE: Articles exercises - THE - definite article

Listening

Practice your listening skills:
Green route: Listening - elementary tests
Red route: Listening: pre-intermediate tests
Orange route: Listening - intermediate tests
Blue route: Listening: upper intermediate tests

Purple route: Listening - advanced tests

More listening:
1. Randall's ESL Cyber Listening Lab 
2. Listening comprehension: A1 t/m B2 level 
3. Activities for Learners | Learning English | Cambridge English
4. Listening comprehension exercises esl - audio stories - podcast (agendaweb.org)

Demonstrative pronouns

Demonstrative pronouns, this/that/these/those
Green route: This that these those - exercises 
Red route: Demonstratives - grammar exercises

Ing-form (gerund) or to infinitive 

When to use an ing-form or gerund and the to infinitive
Blue route: Verbs + to + infinitive and verbs + -ing
Purple route: Verbs + to + infinitive and verbs + -ing

Video

Gerund & to infinitive

Personal pronouns

I - me 
Green route: Personal pronouns exercises - subject pronouns
Red route: Object pronouns exercises - personal pronouns
Orange route: Mixed pronouns - exercises
Possessive pronouns

Me - mine
Genetive case 's: Possessive 's
Possesives: Possessive adjectives 
Possessive pronouns:  Possessive pronouns exercises
Time expressions: Possessive ’s with time expressions

Prepositions

In / on / at
Green route: Prepositions of place and location
Red route: Exercises: prepositions of place and location

Orange route: Prepositions exercises - advanced levels

Prepositions of time

Prepositions of time and place
Green route: Prepositions of time - exercises
Red route: Prepositions of time - exercises level 2
Prepositions of place and movement
Green route: Prepositions of place and location

Orange route: Exercises: prepositions of movement
Blue route: Prepositions exercises - intermediate level
Purple route: Prepositions exercises - advanced level

Quantifier some versus any

First route: Some / any Some / any - grammar exercises
Second route: Something / anything Indefinite pronouns exercises

Quantifiers much versus many

Much, many, (a) few, (a) little  
Countable vs uncountable Countable - uncountable nouns
Quantifiers Quantifiers exercises - quantity words

Reading 

Practice your reading skills: 
1. Reading comprehension exercises - beginner
2. Reading comprehension exercises - elementary 
3. Reading comprehension exercises - elementary
4. Reading comprehension exercises - intermediate 
5. Reading comprehendion exercises - advanced

Word order 

Video word order level A2: Word Order SVOMPT
Video word order level B1: Word Order - Statements

Video word order level B2: Using Only + Word Order

Practice the English word order: 
Word order Word order - grammar exercises