Another site:
AllYESTERDAY'S STATSTop 200 most popular tests to learn English...
1) Present simple (webmaster) 257
2) Look / sound (lucile83) 231
3) Prepositions (anonyme) 220
4) Placement test : grammar for beginners (lucile83) 173
5) Test de niveau anglais (webmaster) 162
6) Preterite (webmaster) 146
7) Greeting and meeting (anonyme) 132
8) Comparatives and Superlatives (anonyme) 122
9) Work environment (anonyme) 120
10) Comparatives / Superlatives (webmaster) 116
11) A/AN (webmaster) 109
12) Modal verbs and use (anonyme) 105
13) Present continuous (webmaster) 100
14) Present perfect or past tense (anonyme) 97
15) So...That / Such...That (anonyme) 97
16) Past simple or present perfect simple (anonyme) 93
17) Interrogative words (anonyme) 86
18) Preterite (webmaster) 85
19) Tenses and verbs (anonyme) 85
20) Comparative and superlative (anonyme) 83
21) Object pronouns (bridg) 82
22) Simple past tense (anonyme) 82
23) Present continuous (webmaster) 81
24) Present simple (webmaster) 79
25) Questions : how to ask them (lucile83) 79
26) Passive form (lucile83) 74
27) Possessive Adjectives (anonyme) 72
28) Him/her/them... (ddec) 71
29) Vocabulary - Placement test (bridg) 70
30) Auxiliary BE (webmaster) 68
31) Verbs and tenses (anonyme) 67
32) Numbers (webmaster) 65
33) Understand and choose (anonyme) 65
34) Could or Couldn't (anonyme) 65
35) Present simple or continuous (lucile83) 63
36) Comparatives (anonyme) 63
37) To be (bridg) 62
38) Words (anonyme) 62
39) Use of words (anonyme) 58
40) Basic but necessary words (anonyme) 56
41) Present simple (lucile83) 55
42) Sport Test (anonyme) 55
43) Right words (anonyme) 55
44) Present perfect continuous (anonyme) 54
45) Present perfect simple (webmaster) 52
46) Used to (bridg) 52
47) My-your-his-etc (ddec) 52
48) Numbers (webmaster) 51
49) Past simple, past continuous or Past perfect (anonyme) 51
50) Possessive adjectives (anonyme) 50
51) Verbs and tenses (anonyme) 50
52) Irregular plurals (bridg) 49
53) Spelled words N°1 (bridg) 49
54) Comparison (komiks) 48
55) Past simple (anonyme) 48
56) There is and there are (tinou) 47
57) Present Simple, Present Continuous, Past Simple (anonyme) 47
58) What time is it? (webmaster) 46
59) Much, many, little and few (felin) 46
60) Connecting words (anonyme) 46
61) Trip to London and past tense (anonyme) 45
62) Understanding of sentences (anonyme) 44
63) Past simple or present perfect (lucile83) 44
64) Past simple or present perfect (lucile83) 44
65) Trade and words (anonyme) 44
66) Adjectives (lucile83) 42
67) The alphabet in English (webmaster) 42
68) Pronouns (woodyrun) 42
69) Reflexive pronouns (bridg) 42
70) Days of the week (bridg) 41
71) Idioms (anonyme) 41
72) Capitals (anonyme) 41
73) Preterite continuous (BE + -ING) (webmaster) 40
74) Pronouns - reflexive and reciprocal (felin) 39
75) Tenses (anonyme) 39
76) There is / there are (bikette329) 39
77) Present simple (komiks) 39
78) Enough with the Present Perfect... (here4u) 39
79) Family life (bridg) 38
80) Present perfect (webmaster) 38
81) Adverbs of frequency (anonyme) 38
82) Words and comprehension (anonyme) 37
83) Riddles (anonyme) 37
84) To be (bridg) 36
85) Scramble Word (anonyme) 36
86) Ask a question (anonyme) 36
87) Antonyms (anonyme) 36
88) Tenses and verbs (anonyme) 35
89) Zero Conditional (necroboynonoss) 35
90) Personal pronouns subjects (bridg) 34
91) Present continuous (chnawa) 34
92) Verb tenses (anonyme) 34
93) There is / There are (anonyme) 34
94) Former - latter/First - last (anonyme) 34
95) Verb Agreement (anonyme) 34
96) Simple past or present perfect (anonyme) 34
97) Present continuous (woodyrun) 33
98) English-speaking country excursion (anonyme) 33
99) Rainy weather (anonyme) 33
100) Much or Many (nounous) 33
101) Comparative of superiority (lucile83) 32
102) Adjectives (woodyrun) 32
103) Past and time clauses (anonyme) 32
104) Tenses and verbs (anonyme) 32
105) Superlative (anonyme) 32
106) Motherhood and pregnancy (baboune16) 32
107) Present perfect (anonyme) 32
108) THE/ A / AN / nothing (webmaster) 31
109) Spelled words N°2 (bridg) 31
110) Relative pronouns (anonyme) 31
111) Verbs and tenses (anonyme) 31
112) To be and tenses (anonyme) 31
113) Present simple (anonyme) 31
114) Two presents: simple and continuous (webmaster) 30
115) Comparative / superlative Adjectives (greg100) 30
116) Input correct form of verb. (anonyme) 30
117) Present simple or continuous (anonyme) 30
118) Adjectives - ed - ing (anonyme) 30
119) Comparative or Superlative (anonyme) 30
120) Two presents: present continuous, present simple (webmaster) 29
121) Adjectives (webmaster) 29
122) Present continuous (tulipe12) 29
123) Weather and Climate (anonyme) 29
124) Contrasting Ideas (anonyme) 29
125) Past simple (anonyme) 29
126) Past perfect or past simple (anonyme) 29
127) Correct form of the verbs (anonyme) 29
128) Prepositions In, On and At (anonyme) 29
129) Present Simple or Continuous or Gerund (anonyme) 29
130) Infinitive clause (lucile83) 28
131) Family (bridg) 28
132) Present continuous OR Present simple? (bridg) 28
133) Past simple tense (anonyme) 28
134) May/might (anonyme) 28
135) Personal and object pronouns (valdyeuse) 28
136) Thanks to...? or Because of...? (here4u) 28
137) What time is it? (webmaster) 27
138) To be - Present (bridg) 27
139) Short placement test (webmaster) 27
140) Tenses and verbs (anonyme) 27
141) Present simple and continuous (anonyme) 27
142) Simple past or Present perfect (anonyme) 27
143) July 4th Barbecue (anonyme) 27
144) Subject pronouns (laure95) 27
145) Family (anonyme) 27
146) Comparatives (webmaster) 26
147) Adverbs of frequency (lucile83) 26
148) Present simple (lucile83) 26
149) Superlatives (frapedur) 26
150) Present continuous (bridg) 26
151) Give your opinion (bridg) 26
152) Possession and 's (florine97) 26
153) Placement test (beginners) (lili73) 26
154) Present perfect or past simple (anonyme) 26
155) Verbs in the Past Tense (anonyme) 26
156) Present simple or continuous (anonyme) 26
157) Tenses of the verbs (anonyme) 26
158) Work out (anonyme) 26
159) Tenses of verbs (anonyme) 26
160) Preterite (webmaster) 25
161) Simple present (bridg) 25
162) Past simple or past continuous (lucile83) 25
163) Future with When,As soon as... (anonyme) 25
164) Past simple (anonyme) 25
165) Open questions (eos17) 25
166) Past simple (anonyme) 25
167) Tenses and verbs (anonyme) 25
168) Possessive adjectives (anonyme) 25
169) Idioms: doctor (webmaster) 24
170) Present perfect simple (bridg) 24
171) Possessive adjectives (jagienka) 24
172) Family tree (anonyme) 24
173) Answering questions (anonyme) 24
174) Comparative with Less (lemagemasque) 24
175) Verbs and conjugation (anonyme) 24
176) Plural of nouns (anonyme) 24
177) Personal pronouns (valdyeuse) 24
178) Who or Whom (anonyme) 24
179) Word search (anonyme) 24
180) Used to - Be Used to - Get used to (anonyme) 24
181) Present Simple vs. Past Simple (anonyme) 24
182) Preterite: simple or continuous? (webmaster) 23
183) Adjectives - ing and ed (felin) 23
184) Modals (webmaster) 23
185) Past simple (video) (lucile83) 23
186) Active and passive form (anonyme) 23
187) Past simple (anonyme) 23
188) Alternative medicine (baboune16) 23
189) Do/does/did/done (mariofrank) 23
190) How to pronounce the final -ED? (past simple) (webmaster) 22
191) Plural (webmaster) 22
192) Comparatives of superiority (lili73) 22
193) Be allowed to (laure95) 22
194) Comparative (lucile83) 22
195) Come vs. Go (anonyme) 22
196) Grammatical tense (anonyme) 22
197) Vocabulary and sale (anonyme) 22
198) Missing words (anonyme) 22
199) Question Tags (anuesther) 22
200) History of the USA (anonyme) 22
