You should check the sd cards first.
Then disable all desktop applets. Reenable one by one, testing for a while in between. One of them may leak causing hildon-desktop to grow.
Monitor each process memory usage in a xterm with top, or better with procps's top, or use the panel applet, see what's growing.
Also, check the usage of the swap devices with 'cat /proc/swaps', DT has a ramzswap device of 96M, which should be enough for most usage saving the swap file for the most extreme cases. I usually don't go over 60 MB of swap usage.
Deleting unrelated programs won't help you.