I'm using the latest Bukkit Dev build (the stable version isn't supported for the latest minecraft) and I am hosting my server on a VPS with 2GB of RAM, Six-Core AMD Opteron(tm) Processor 2.00GHz, and my server is constantly at 100% CPU. I have ChatManager, ChestShop, Essentials, iConomy, LogBlock, LWC, mcMMO, ModifyWorld, NoCheat, PermissionsEx, PluginMetrics, Prism, SafeExplosions, SetRankPEX, Votifier, WorldEdit and WorldGuard plugins installed on my server. I've tried just about everything to fix this problem.
Your CPU looks a little weak to be running a minecraft server. Minecraft is still primarily single threaded, so most of the load will be on one core. It is not uncommon to see 70-90% cpu usage on the main core. More cores is better for most things, but not minecraft servers. What you can do: Get a CPU with a higher clock rate Remove/optimize plugins (if you need help with this you should post timings)
