Someone else will be able to help you with birds better than me, but for small animals like hamsters, gerbils and mice, the toys on these 2 pages are perfect:
http://www.littlepetwarehouse.co.uk/...il-mouse-toys/
Particular favourites are the wooden bendy bridges, grassy tunnels, wooden houses, log tunnel and the cheese house.
Tubes like these are also a big hit as they double as a chew toy and come in different sizes for different small pets:
http://www.smallpetz.co.uk/boredom-b...ube-small.html
And these:
http://www.smallpetz.co.uk/boredom-b...log-small.html
http://www.smallpetz.co.uk/boredom-b...imb-kit-4.html
Plus chew toys, which are vital, because small animal's teeth grow constantly and chewing suitable toys and chews help keep them the right length:
http://www.smallpetz.co.uk/small-pets-activity/page-4/
And for some beneficial healthy treats which go down very, very well, the Boredom Breakers' range is extremely good and suitable for a variety of small pets so they can be shared around:
http://www.smallpetz.co.uk/small-pets-treats/page-2/
Finally, hamsters and mice love wheels so if you want to add one, these are the best and cheapest you will get that are the right size:
http://t.zooplus.co.uk/shop/small_pe..._wheels/174195
And gerbils adore tunnels and cardboard and will delightedly destroy as many kitchen/ toilet roll tubes and poster tubes as you can fit in their tank, so if your rescue place has gerbils in they would be a very cheap and excellent donation.
All of these things I have bought myself at one point or another for my own pets. Their safe, well recommended and you won't go wrong with any of them

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