Joblow - You can checkout the website
www.enjoyshanghai.com or
www.smartshanghai.com they both provide good information about SH in terms of clubs, restaurants, shopping etc.
If you want to buy electronics (personally I rather buy in HK) you can go to Xujiahui thats located on Metro line 1 that place will take you at least a day to walk everything.
You can go to The Bund, People Square, Nanjing Road (both east and west), Yu Garden, Xintiandi, Pudong Jinmao Tower, Pearl Tower and there are a lot more things that you can do I am probably missing. But honestly most of the time you are just going to be eating. I personally thinks eating in SH is better than HK now. If you want shopping than stay in HK.
PM if you have any other questions.