YAROS

Ragnarok Online tools and calculators:
Keio Skill Simulator - A decent Skill Simulator (including classes such as Taekwon and Ninja)
Ragnarok Character Simulator - Create an image of a RO-character by choosing class, hairstyle etc.
Ragnarok Upgrade Price Calculator - Estimates the price upgrading a weapon costs
http://calcx.wushuang.ws - Complete character calculator (incl. gear, stats, skills etc.)

Ragnarok Online guides and tips:
iRO Wiki - Tons of information about pretty much any aspect of Ragnarok Online
Ragnarok Online Helpdesk - Class guides and quest tutorials

Ragnarok Online item / monster / quest databases:
RateMyServer.net - Contains database with Items, Monsters, Skills, Etc. (Our Server Listing)

Our voting sites:
Top G.org - (Voting page here)
Top 100 Arena - (Voting page here)
Top 200.gs - (Voting page here)
RO Toplist - (Voting page here)
Mega Top 200 - (Voting page here)
Ragnatop.com - (Voting page here)
Apex Webgaming - (Voting page here)
Online Top 100 - (Voting page here)

Game related sites
VG Reloaded - The Home of Gaming on the web!
Smash Mansion - A Nintendo Fansite.
Nintendo Gal - One-stop shopping for Nintendo news with witty remarks.
Game Lemon - Grab your games by the horns!
Game Observer - Gaming by profession.
Startmenus Games - Dutch overview of gaming-related sites.

Other Link Partners:
ExchangeLinksOnline
Link Directory | Add your link for free | LinkDirectory
eDirectories
dmozlist.com Internet Directory - Submit your site FREE. Drive quality Traffic
Add your link

Special thanks to NeSsARaE, Fox_T4il and Necrophiliac for contributing to this topic.

If you have any additions to this list, don't hesitate to list it in a reply or private message.