I recently learned about A+ Click Math thanks to Craig Barton who describes the site very clearly in the video below. Choose by topic or by age from this extensive collection of problems; all are multiple choice, include solutions and will display well on the interactive whiteboard. As Craig suggests these would make great starters. This is an outstanding site and not a single advert in sight! As part of my never ending quest to make sure I can find things again I have added this site to my Collections page on Mathematics Starters and Plenaries.
Note that the video is number 29 of the series of Web Whizz videos where Craig looks at a different website each week. These videos are available on the TES Resources site which I included in my Top>10 Mathematics Websites.
On the subject of TES Resources, do explore the site if you have not done so. Registration is free and many high quality resources are available. Start at the Secondary Maths page for resources for students age 11-18 and the Primary pages for younger children: Key Stage 1 and Key Stage 2.
Note the very useful collections page on the Secondary page which organises resources into groups. There are several new Topic Specials where members of the newly formed TES Maths panel, of which I am very pleased to be a member have picked their favourite TES resources for teaching a variety of topics.
You can follow the Secondary Maths panel using this Twitter list.