The following GMAT idioms list is based upon official GMAT sentence correction questions that the test-makers publicly released.
Practice these idioms using our proprietary sentence correction questions.
GMAT Idiom Book1 Question2 Answer Page3 Official Guide for GMAT Review (12th Edition) x is more than y 12th Edition 4 686 unlike x, y 12th Edition 20 694 in contrast with x, y 12th Edition 20 694 in contrast to x, y 12th Edition 20 694 estimate to be 12th Edition 27 698 the same to x as to y 12th Edition 32 700 depends on whether x 12th Edition 34 701 so x that y 12th Edition 37 702 targeted ... at 12th Edition 40 704 rivalry between x and y 12th Edition 44 706 expended on 12th Edition 46 707 the ability ... to 12th Edition 51 710 x is to y what w is to z 12th Edition 58 714 amount of x 12th Edition 74 722 attributes x to y 12th Edition 79 724 not just because of x, but because of y 12th Edition 83 726 distinctions between x and y 12th Edition 96 733 either x or y 12th Edition 109 740 to consider x y 12th Edition 117 745 less successful than 12th Edition 123 748 so x that y 12th Edition 124 748 x is dated at z years old 12th Edition 140 756 Official Guide for GMAT Review (11th Edition) x is more than y 11th Edition 2 662 in contrast with x, y 11th Edition 16 669 estimated to be 11th Edition 21 671 in danger of 11th Edition 27 673 seem + infinitive 11th Edition 29 674 as much as 11th Edition 30 674 to credit x with 11th Edition 31 674 as many ... as 11th Edition 37 676 between x and y 11th Edition 40 678 require x to do y 11th Edition 53 684 restrictions on x 11th Edition 54 685 not only x ... but also y 11th Edition 55 685 there is no doubt that 11th Edition 58 686 as a means to 11th Edition 60 688 attribute x to y 11th Edition 67 691 as many as 11th Edition 76 695 used x as y 11th Edition 79 696 not x, but rather y 11th Edition 87 700 order x to be y 11th Edition 92 702 just as x, so y 11th Edition 99 706 distinguish between x and y 11th Edition 107 710 both x and y 11th Edition 112 713 so x that y 11th Edition 118 716 Official Guide for GMAT Verbal Review not...but Verbal Review 4 256 the rising cost Verbal Review 8 258 range from x to y Verbal Review 9 258 except for + noun Verbal Review 13 260 between x and y Verbal Review 14 260 to mistake x for y Verbal Review 17 261 to think of x as y Verbal Review 20 262 with the aim of + (verb)ing Verbal Review 25 264 not only x ... but also y Verbal Review 46 274 prohibit x from doing y Verbal Review 48 275 more x than y Verbal Review 50 276 not only x ... but also y Verbal Review 52 277 so x that y Verbal Review 58 280 not x, but rather y Verbal Review 60 281 not only ... but also Verbal Review 66 284 in order to x Verbal Review 69 285 as x as Verbal Review 75 288 worried about Verbal Review 81 291 either x or y Verbal Review 84 292 better served by x than by y Verbal Review 89 295 ordered x to do y Verbal Review 90 295 both x and y Verbal Review 93 297 x rose almost as fast as y Verbal Review 94 297 between x and y Verbal Review 95 298 more x than y Verbal Review 98 299 x rather than y Verbal Review 99 300 isolated from Verbal Review 106 300 not only x ... but also y Verbal Review 108 304 as a result of Verbal Review 113 307 This GMAT idioms list is available in PDF format.
For those who are too cheap to buy himself or herself a copy of Manhattan GMAT "Sentence Correction GMAT Preparation Guide", here is the list of the most popular GMAT idioms that are likely already known by native speakers, and must be memorized by non-native speakers (like I am).
http://www.amazon.com/exec/obidos/ASIN/0982423861/iwhite-20
For those who do own a book, take a look at chapter 9, page 142. I am not sure I would be able to memorize all that, but at least I have one more useful guide to refer to.