use adw launcher it is the best homescreen by miles, once you get used to it all others will seem pointless, stick to a minimal amount of widgets and a max of 3 screens.
a good task manager I've found is task panel x. it gives you a widget for your homescreen with a kill all button and has ignore and autokill options to keep things running smoothly
avoid live wallpapers like the plague, try using something like wallswitch instead to auto change your wallpapers. there are loads of apps to get nice wallpapers and most of them look miles better than the gimmicky live wallpapers anyway.
I have spent hours trying out every widget and app out there and can highly recommend the following...
My current widgets
countdown timer widget,
mort player music widget,
sticky pad pro widget (totally customizable and great for shopping lists)
guage battery widget
digital clock widget
system panel light (best looking task manager by far)
app brain (better than the market)
chrome to phone
ezpdf reader (has night mode)
laputa (excellent free ebook reader)
myplayer (old version still works)
Slideit keyboard (like swype but much better)
uk tv droid (excellent tv guide with reminders)
Uloops studio (THIS ROCKS, BEST ANDROID APP EVER)
if anybody knows of any better alternatives to these I would love to hear about them.