More speed (responsiveness) for the linux desktop

Ram and file system cache:

vm.swappiness=20
vm.vfs_cache_pressure=50
more info

Preload most used applications/libs:

preload 
more info

Mounting /tmp to RAM

add this to your fstab:

tmpfs /tmp tmpfs defaults,noatime,nodev,nosuid,mode=1777 0 0

more info

BFS Kernel

There is a set of kernel patches that increases the responsiveness of the linux desktop. This is not limited to archlinux btw.

There are two main ways to get it on archlinux:
Build it from AUR: yaourt -S linux-ck

Or us a repository with precompiled packages:

[repo-ck]
Server = http://repo-ck.com/$arch

more info