Hi Runoutofideas:
Aside from the local library Summer reading challenges, I'd suggest the following:
If you haven't come across it yet - The BBC has a new website (still BETA version) called BBC Learning www.bbc.co.uk/learning/ - from this opening page, on the right click Teachers box (olive green) and then you'll see an orange outlined box midway down on left with EYFS, KS1 and KS2 tabs - from what you've said it sounds like your DD is ready for KS2 work (ages 7 - 9) so click the KS2 tab. You can then select support materials by curriculum topic.
KS2 Literacy worksheets here: www.bbc.co.uk/schools/teachers/keystage_2/topics/literacy.shtml. There are a lot of Tracy Beaker literacy support packs. If your DD likes this show, she may respond well to these writing exercises.
You'll notice that on KS2 literacy - there are also activities tab and games tab - so there is a lot more than worksheets.
Oxford Owl www.oxfordowl.co.uk/ - also has e-books, games and all sorts of ideas to support reading (your DD would probably fall into 'older reader' (ages 7 - 11) category from what you've said).
Other writing ideas during the summer include:
entering competitions (a lot of book series - i.e. Rainbow Magic Fairy series - and magazines have competitons. Also the range of comopetitions with children's tv - all of these can be entered by writing in).
Write to favourite author telling them how much you enjoyed the story, maybe also sending in a drawing.
National Trust/ English Heritage have a lot of 'trails' and 'quizzes' at their sites over the summer.
Postcards - great to send to friends or teachers. Just ensure that it is more than one sentence greeting.
Have your DD keep a journal or log book and record her summer's observations. [we find this works best if DDs chose the notebook and a special pen or pencil for the job]. You can record all sorts of things: How much rain fell between August 1st - September 1st. Record daily temperatures, wild life (count butterflies and identify them - find out more about what plants they need for nectar and what plants they lay their eggs on). Study hover flies or dragon/ damson flies. Study pools (fresh or salt water). Record flowers and find out what they were used for. All this kind of thing is great on building science skills, but also gets lots of writing done and builds vocabulary. Record when you first notice ripe blackberries. Record how long it takes a plant (or several different plants) to go from flower to seed head.
All great practice.
HTH and have a great summer