Hi, Jo44,
I've been teaching ESL/EFL for several years. If you are teaching prepositions, I recommend the following activities:
1). Google the lyrics of "Octopus' Garden" by the Beatles. Create a cloze activity worksheet with the prepositions (there are a TON in that song!).
2). (This activity works well with a group or kids/teenagers especially, it's kind of like TPR activity): When they are familiar with the basic prepositions (on, next to, in, etc.), tell them, "Okay, put your book
on your head. Place your left foot
under your chair, etc." It creates a humorous situation that is more effective than just a worksheet.
For good websites, I highly recommend
www.onestopenglish.com. Although you need a paid subscription (around US$64 annually), it is a gold mine. Imagine you enter some VERY specific criteria for your lesson (let's stay you select the options that you will be teaching a 60 MINUTE LESSON to ADULT LEARNERS with an INTERMEDIATE LEVEL focusing on VOCABULARY)... The site will search its data base and show you what lessons and activities it has based (among thousands) that match your needs. Pretty cool stuff.
PM me if you have any questions about anything else ESL-related, the field is truly my passion. Saludos!