Blowing bubbles is my number one favorite toddler activity. It's such a simple activity, but most toddler's go crazy for bubbles. I've worked with more toddler's who have said 'more' as one of their first words, while we played with bubbles, than I can count! When you break out the bubbles, language learning can happen right from the start. I usually give children the unopened bottle of bubbles so that they can try to open it before handing it back to me for 'help'. *Note* It's a good idea to have 2 containers of bubbles on hand because most children will shake up the container of bubbles they're given, and good luck blowing a bubble after that!
I model the word 'open' very slowly as I open the bubbles and tell them I'm going to 'blow.' Once you blow some bubbles, show children how to 'pop' them and model the word over and over again. Of course once all the bubbles are gone, they're going to want 'more' so this activity can last a very long time! When bubble play is over, put the bubbles out of your child's sight, otherwise they're likely to ask for bubbles all the time!
One warning, not all bubbles are created equal, I've test-drove many different brands and haven't yet found one that is consistently good! Fortunately, bubbles are cheap and can be made at home as well. If you buy a dud, just replace the bottle the next time you shop.