For many of these websites, you can make your own quizzes or browse and use ones other people have made. Alternatively, if your school allows students to set up accounts in external websites, get your students to make their own quizzes.
Kahoot allows you to create quizzes (or browse and use other teachers' ones). The teacher controls the progression of questions on the IWB, and the students use mobile devices to choose answers. Make sure you are on the right website - create or find questions on kahoot.com and get students to log in to kahoot.it or download the app.
Socrative is similar, but the students work at their own pace on the questions (although they can see their progression as a race on the IWB).
Quizlet and Quizalize
Quizlet allows you to create flashcards and play a variety of games with these. I like the matching game (for teams of students at the IWB or for homework) and Quizlet Live, which works a little like Kahoot. Quizalize (also known as Zzish) is a website which allows you to import Quizlet flashcards to play with your students in other formats.
I've mentioned Quizbusters in the games section on this site. You can browse for ready made quizzes or make your own. It has the advantage that you don't have to log in (or remember passwords), but you will need to save the address of the page you create, and if you make a mistake typing the questions, you can't go back in and fix it once you've finished editing. However, in 2020 Adobe ended support for Flash Player which means that it will be much harder to access these games now.
Finally, Hot Potatoes is free downloadable software which lets you create quizzes (e.g. drag and drop matching, crosswords, gap fills) easily, and then publish them online (e.g. in your college's virtual learning environment). It looks a little old-fashioned nowadays, but the quizzes work very well for language practice as homework and you can play with the colours and fonts to make it a little more appealing.