Suspend to RAM is useful with Laptops and Netbooks, these days batteries last a lot, but anyway not enough if you leave your computer running on batteries while you are not working on it.
Linux distributions like Ubuntu, Peppermint, Mint, Fedora and other alike may have automatic support for this by just closing the lid of the Laptop, Netbook.
For Slackware users
echo -n mem > /sys/power/state
For Arch Linux users
echo -n standby > /sys/power/state
This from the console, of course if you are using Slackware or Arch Linux, you are not afraid of the console commands.
The computer should start once you open the lid.
Note: I am using default distribution Kernels 2.6.33 and 2.6.35 on Slack and Arch