Sophos provide an AV solution for Linux but I don't know if it works on Maemo. But you should remember AV for Mac and Linux is really only there to stop you passing on Viruses to Windows users as few genuine viri exist for Unix type platforms.
If you're going to be passing files from your N810/N800 to a Windows machine then isn't your AV solution there going to spot infected files anyway?
Personally, the N810's processor is too slow as is. I don't want it slowed down further by an AV program.
ClamAV comes to mind, but there are *no known* viruses in the wild for Linux and definitely not any for ARM Linux. ClamAV is open source so it shouldn't be a problem to compile it and run it on your N8x0 but it will only find *Windows viruses.*
Also, please describe what a "RAM cleaning program" does. I'm not sure I understand...
@ Johnx,
I mean with RAM-Cleaning programm the same programms in PC like TuneUp Utilities 2007 or some think like that, which clean the temporary files and the doppel- files ...etc.