Which remote help solution?

[Mitja Podreka <liste@kitaj.net>]

Hello.

I've migrated three friends to Linux. To make their (and mine) 
experience more pleasant I would like to be able to remotely access 
their computer and if possible enable them to see what I'm doing. The 
problem is that they are all behind router and I cannot expect from them 
to start some complicate procedure to enable me to connect remotely to 
their computer.
Googling around I couldn't find any apparent (easy) solution. I don't 
mind setting up and learning, just I would not like to waste my time for 
wrong bad.
Could you please suggest me some approach or just tell me what you're 
using for remote help.

Thanks,
Mitja