Another site:
AllTODAY'S STATSTop 200 most popular tests to learn English...
1) Preterite (webmaster) 200 2) Present simple (webmaster) 197 3) Passive form (lucile83) 159 4) Present perfect simple (webmaster) 156 5) Past perfect (lili73) 142 6) Modals (webmaster) 116 7) Simple present (bridg) 111 8) Comparatives / Superlatives (webmaster) 110 9) Present continuous (webmaster) 100 10) Verbs with two object complements (here4u) 99 11) Superlative Adjectives (bridg) 88 12) Present simple (webmaster) 86 13) Past simple or present perfect (lucile83) 78 14) Present perfect (webmaster) 75 15) Placement test : grammar for beginners (lucile83) 72 16) Could - Should (lili73) 72 17) Past perfect simple or past simple (necroboynonoss) 71 18) Preterite (webmaster) 65 19) (lemarseillais) 57 20) Much, many, little and few (felin) 56 21) A/AN (webmaster) 54 22) Past simple or past continuous (lucile83) 54 23) Preterite continuous (BE + -ING) (webmaster) 53 24) Preterite (webmaster) 50 25) Present perfect simple (bridg) 48 26) Past simple or present perfect (lucile83) 46 27) Present simple (lucile83) 45 28) Past perfect simple or past simple (necroboynonoss) 45 29) Past perfect tense (sreedhar) 44 30) Possessive case (valdyeuse) 43 31) Test de niveau anglais (webmaster) 39 32) THE/ A / AN / nothing (webmaster) 39 33) 2 Preterites (webmaster) 39 34) Make/get/have (woodyrun) 37 35) Conditional 1 (necroboynonoss) 37 36) Present continuous (webmaster) 35 37) Can/Could (matrixhamdi) 35 38) Compound words with some,any... (woodyrun) 34 39) Not or no ? (lucile83) 33 40) Dictation : April Fool's Day (webmaster) 32 41) Modal verbs (bridg) 30 42) Vocabulary - Placement test (bridg) 29 43) Plural (webmaster) 28 44) How much/how many (woodyrun) 28 45) Possession and 's (florine97) 28 46) Do / Make (bridg) 27 47) Pronunciation of final S (lili73) 27 48) Comparison (komiks) 27 49) Verbs in the -ing form, or not? (here4u) 27 50) Much/many or a few/a little. (felin) 26 51) "Both" and its use (lucile83) 26 52) Could/Couldn't (laure95) 26 53) Was - Were (benstrong) 26 54) (bridg) 25 55) Passive voice (webmaster) 25 56) Superlatives (frapedur) 25 57) Can/Must/Should (laure95) 25 58) Irregular verbs (bridg) 24 59) Articles : a or an (lucile83) 24 60) Questions and past tense (laure95) 24 61) Past simple or past perfect simple (necroboynonoss) 24 62) Modal auxiliaries in the past. (here4u) 24 63) Preterite: simple or continuous? (webmaster) 23 64) Some / Any / no... (bridg) 23 65) Adverbs of frequency (lucile83) 23 66) Comparatives (webmaster) 22 67) Present simple or continuous (lucile83) 22 68) Past simple (video) (lucile83) 22 69) Modals: should, would, could (carlabice47) 22 70) Make sb do sth or have something done (flori10) 21 71) For,since and ago (lucile83) 20 72) Can, could and be able to. (felin) 20 73) What time is it? (webmaster) 19 74) Past tenses (bridg) 19 75) Pronouns (woodyrun) 19 76) Present simple (lucile83) 19 77) Present simple (komiks) 19 78) Zero Conditional (necroboynonoss) 19 79) Can / could/ may/ might (woodyrun) 18 80) Articles and letters h and u (lili73) 18 81) Infinitives (here4u) 18 82) Countries & nationalities (bridg) 17 83) Auxiliary BE (webmaster) 16 84) Superlatives (webmaster) 16 85) Make, Have, Let (bridg) 16 86) Indirect speech (bridg) 16 87) Conditional clauses (lucile83) 16 88) At the station - Taking the train (bridg) 16 89) Numbers (webmaster) 15 90) There is / there are (bikette329) 15 91) Direct and indirect speech (lili73) 15 92) Two presents: present continuous, present simple (webmaster) 14 93) Adjectives (webmaster) 14 94) Adverbs of Frequency (bridg) 14 95) Prefixes (1) (felin) 14 96) IN, ON, AT or TO? (webmaster) 14 97) (bridg) 14 98) Irregular verbs (lili73) 14 99) Be in the simple past tense (lucile83) 14 100) Describing a picture (lili73) 14 101) CAN / MUST (webmaster) 13 102) Frequency adverbs (webmaster) 13 103) Modals (tinou) 13 104) Irregular plurals (bridg) 13 105) What time is it? (webmaster) 13 106) Comparative of superiority (lucile83) 13 107) Short placement test (webmaster) 13 108) Ask questions (chnawa) 13 109) Conditional 2 (zilazila) 13 110) Did, was or were (laure95) 13 111) Numbers (webmaster) 12 112) To be (bridg) 12 113) Comparing (webmaster) 12 114) Infinitive clause (lucile83) 12 115) Plural forms (bridg) 12 116) About the weather (lucile83) 12 117) Must or Have to? (woodyrun) 12 118) 200 irregular verbs and audio (bridg) 12 119) Prefer/rather (bridg) 12 120) Some, any, no, enough, too/too much/too many (webmaster) 11 121) Countable or Uncountable? (webmaster) 11 122) Conditional (webmaster) 11 123) Adjectives (lucile83) 11 124) Modal can (video) (lucile83) 11 125) Present continuous (woodyrun) 11 126) Words and suffixes (bridg) 11 127) Adverbs of frequency (lili73) 11 128) Present perfect simple / continuous / Past tense (taiji43) 11 129) Dictation - Arcimboldo - 1 - (2) (denis76) 11 130) General Test II / End of high school / Beginning of universi (webmaster) 10 131) Modals (webmaster) 10 132) Relative pronouns (webmaster) 10 133) Used to/would (woodyrun) 10 134) Much or many (matrixhamdi) 10 135) (lili73) 10 136) No/None .... (brettdallen) 10 137) Express the future (lili73) 10 138) To / in order to / so as to / so that (irish21) 10 139) Social networking sites (rkjs58) 10 140) General test-End of high school / Beginning of university (webmaster) 9 141) Present BE + Ving (bridg) 9 142) How to pronounce the final -ED? (past simple) (webmaster) 9 143) (bridg) 9 144) Do or Make? (lucile83) 9 145) I wish, if only (felin) 9 146) Spelled words N°1 (bridg) 9 147) Present continuous (chnawa) 9 148) Passive form (lucile83) 9 149) Future simple (lucile83) 9 150) Revision (lili73) 9 151) If clauses (laure95) 9 152) Present perfect or past perfect (laure95) 9 153) Do or Make (aoma92) 9 154) Simple past tense (sreedhar) 9 155) Placement test (beginners) (lili73) 9 156) Computers - vocabulary (lili73) 9 157) Absence of obligation (here4u) 9 158) Can't or Mustn't (here4u) 9 159) Modal Auxiliaries (zilazila) 9 160) Can - can't - could - couldn't (here4u) 9 161) Bring or take (here4u) 9 162) Two presents: simple and continuous (webmaster) 8 163) Genitive (webmaster) 8 164) A/an/Ø (bridg) 8 165) Agreement Tags (webmaster) 8 166) Preterite (bridg) 8 167) 'The' or nothing? (webmaster) 8 168) Abreviations (webmaster) 8 169) Genitive case (bridg) 8 170) Personal pronouns subjects (bridg) 8 171) Present continuous or present simple (webmaster) 8 172) Present Simple (anuesther) 8 173) Some / any (younes91) 8 174) Relative pronoun (bridg) 8 175) Health / illness (felin) 8 176) Possessive adjectives (jagienka) 8 177) Conditional with 'if' 2 (lili73) 8 178) Do , does , did (jagienka) 8 179) Give your opinion (bridg) 8 180) Past perfect simple or continuous (lucile83) 8 181) Reflexive pronouns (bridg) 8 182) Present simple or continuous (valdyeuse) 8 183) Modal Verbs of Permission and Obligation (greg100) 8 184) Must or mustn't (laure95) 8 185) How many - How much (valdyeuse) 8 186) Compound adjectives for beginners (here4u) 8 187) Future (webmaster) 7 188) 2 presents (webmaster) 7 189) Introducing oneself (webmaster) 7 190) (webmaster) 7 191) Which modal and when ? (bridg) 7 192) Infinitive proposition (lucile83) 7 193) How to ask a question in English (bridg) 7 194) (felin) 7 195) There is / there are (lucile83) 7 196) Past tense in the interrogative form (woodyrun) 7 197) Object pronouns (bridg) 7 198) The alphabet in English (webmaster) 7 199) Modal verbs (antoniutti) 7 200) Relative pronouns: Who/whose/whom/which/of which (bridg) 7