Have been reading the topics about discovery bottles and would love to do them with my class next week. Was just wondering what are the most popular ( and to begin with ) the easiest ones to do to to start with? Any suggestions woudl be greatly appreciated.

I'm a big fan of half coloured water, half oil. ~ (i don't fill the bottles right to the top, leaving space for the water and oil to mix when shaken).
sound shakers are also nice - put some pasta or lentils etc in.

other ideas:
feathers, ribbons, glitter

We had marbles in water and another with marbles in shampoo - they liked the difference each gave. They also liked the 2 litre one with water, colouring and some washing up liquid - it just makes so many bubbles. We also have a float/sink one, with 6 items in.

plastic bugs, small under the sea things, sequins and glitter in glycerine was popular

we did this for a parents workshop and it was a great success. We used all sorts-
water and hair gel,
glycerine (or baby oil, water and glitter)
sand and objects that are magnetic- use a magnet to search for them in the sand,
punch holes in the plastic bottle, add pot porri and hey presto a smelly one
oil, water - wrap tin foil around very small stones and screw up tin foil balls to make them lighter than the stones. When the children turn the bottles upside some sink and sone float. Adding oi makes the water heavier and acts like a lava lamp so slows the process down slightly.
Small bottle filled with iron filings (if you can find any)

The only thing I would recommend is making sure you glue gun the lids on or use Araldite which is far stronger- some children are very inquisitive and took the lids off spilling the contents everywhere!

I am sure you have already done a search but here are a few just in case- I like the first one as it has pictures

http://www.kinderfriends.com/discoverybottles.html

http://teachers.net/lessons/posts/2844.html
http://teachers.net/lessons/posts/422.html

thank you so much for all the lovely ideas - i am now really inspired! xx

If you have bigger bottle you can do them for different songs - Twinkle Twinkle can have foam stars and glitter etc. Don;t do an Old Macdonald one with farm animals and blue water - it is freaky! A Childrens Centre near me did that!