As for projects created using current CLI Tools, it worked for me by installing

npm install angular-in-memory-web-api --save

and then performing import as

import { InMemoryWebApiModule } from 'angular-in-memory-web-api/in-memory-web-api.module';

My package.json

> "dependencies": {
>     "@angular/common": "^2.4.0",
>     "@angular/compiler": "^2.4.0",
>     "@angular/core": "^2.4.0",
>     "@angular/forms": "^2.4.0",
>     "@angular/http": "^2.4.0",
>     "@angular/platform-browser": "^2.4.0",
>     "@angular/platform-browser-dynamic": "^2.4.0",
>     "@angular/router": "^3.4.0",
>     "angular-in-memory-web-api": "^0.3.1",
>     "core-js": "^2.4.1",
>     "rxjs": "^5.1.0",
>     "zone.js": "^0.7.6"   },

>     "devDependencies": {
>     "@angular/cli": "1.0.0-rc.4",
>     "@angular/compiler-cli": "^2.4.0",
>     "@types/jasmine": "2.5.38",
>     "@types/node": "~6.0.60",
>     "codelyzer": "~2.0.0",
>     "jasmine-core": "~2.5.2",
>     "jasmine-spec-reporter": "~3.2.0",
>     "karma": "~1.4.1",
>     "karma-chrome-launcher": "~2.0.0",
>     "karma-cli": "~1.0.1",
>     "karma-jasmine": "~1.1.0",
>     "karma-jasmine-html-reporter": "^0.2.2",
>     "karma-coverage-istanbul-reporter": "^0.2.0",
>     "protractor": "~5.1.0",
>     "ts-node": "~2.0.0",
>     "tslint": "~4.5.0",
>     "typescript": "~2.0.0"   }