SHAKE A BABY
The most useful subnetting cheat sheet ever (IPv4 and IPv6). Expanded upon from krow.net NOW INCLUDING IPv6
MXToolbox:Utilities for diagnosing mailserver issues.
IntoDNS: An exceptional dns health check utility
Fixed Orbit: AS Lookup tools <-- lots of stale data on here, but somewhat useful still...
Filter List Generator: Prefix list generation website for various routers
SuperWhois: Advanced Lookup
Outages Dashboard:good list of ways to find "what is down"
TraceRoute.org: Super Cool Page with lots of utilities, including Free Access Public Telnet Servers for traceroute help, as well as LookingGlass reports and BGP Tools
Arin: Whois Lookup Page (works for IP and ASN lookups)
InterNic: Whois Lookup
KeyNote: Internet Health Report (North America Only)
PowerDNS: A very powerful DNS Server supporting multiple backend technologies and modules (yes I use it for all my nameservers)
CleanWipe: A utility for completely removing Symantec Anti-Virus when the normal uninstaller fails or generally gives you the finger.
HP Insight Foundation Download: This page has the majrity of HP Tool downloads
HP ESXi5 Download: This page launches the downloader for the ESXi image with the HP Tool preloaded
Dell R610 ESXi5 Download:This page contains the downloads for the R610 ESXi installer (works for everything dell with preloaded tools)
Dell OpenManage for ESXi 5.x and VIBs:This page contains the downloads for Dell OpenManage and the ESXi VIB
Dell OpenManage for ESXi 5.x Install Guide:Open Manage Install Guide