Valk Space Reclaimer is "one-button", in a sense -- you just have to run it, and it can stop all programs, free memory, etc.
MemMaid offers more options, more fine-tuning control, but is also more dangerous if you don't know what you're doing with it
Space Reclaimer is easier for novices to use, requires almost no setup, and it can be programmed to automatically exit after running. It can also be programmed to run automatically after soft reset.
I have no idea about the relative effectiveness of these programs. I know they both free up memory, because I've used them successfully, freeing up as much as 3 MB in one run.
I have not tried Oxios Memory, but it doesn't appear that it's been released for WM5 yet (there's an alpha version on the web page).