add links to useful external tools

README.md

@@ -6,13 +6,27 @@ This is repository shows a few tools we use to gather intelligence on (possible)
 
 They are designed to be passive/quiet and utilize open-source information. (OSINT)
 
+----
+
+## External Tools and Providers
+
+* [IPInfo](https://ipinfo.io)
+* [Shodan Internet Search-Engine](https://www.shodan.io/search)
+* [CenSys Internet Search-Engine](https://search.censys.io/search)
+* [Certificate Search](https://crt.sh/) ([GitHub](https://github.com/crtsh))
+* [projectdiscovery - tool collection](https://github.com/projectdiscovery)
+* [cloud.projectdiscovery.io](https://cloud.projectdiscovery.io) Platform
+* [TheHarvester](https://github.com/laramies/theHarvester) util
+
+----
+
 ## DNS
 
 See: [README](https://github.com/O-X-L/offsec-recon/blob/main/dns/README.md)
 
 ## IPs
 
-See: [README](https://github.com/O-X-L/offsec-recon/blob/main/ips/README.md)
+See: [README](https://github.com/O-X-L/offsec-recon/blob/main/ip/README.md)
 
 ## Web Crawler - Quiet via PyAutoGUI