Not really... ther are memory monitoring apps that you could try to deduce where the memory is going to but it would be hit and miss, and I assume you are closing them correctly (from the menu)?
Otherwise the only way is to strip all of the third party apps from your device and start re-installing them one by one and running each for a day or so before installing more, this should show up any memory hog...
Here are my apps
Amazon
CB App Store
BB App World
Chicago Cubs
CB Mobile
Car GPS
ESPN
Mapquest
OpenTable
Poynt
Score
TWC
Ticketmaster
Tip Calculator
QuickPull Pro
BerryBuzz
Berry Weather
Google Mobile
Yahoo Mobile
Guitar Hero III
Solitaire
Mahjong