A short reasoned selection from my bookmarks

RobTex

DNSLookup, Domain informations,Network informations

[embed]https://www.robtex.com/[/embed]

Shodan

Search engine used to find Internet of Things (IoT) connected devices around the world: reports open port and services.

[embed]https://www.shodan.io/[/embed]

Network-Tools.com

Several online services, including domain lookup, IP lookup, whois, traceroute, URL decode/encode, HTTP headers and SPAM blocking list.

[embed]http://network-tools.com/[/embed]

CentralOps Free Online Network Tools

Domain checker and other advanced internet utilities

[embed]http://centralops.net/co/[/embed]

UrlQuery

Service for detecting and analyzing web-based malware

https://urlquery.net/index.php

Sucuri Sitecheck

Service for detecting and analyzing web-based malware

[embed]https://sitecheck.sucuri.net/[/embed]

Web Inspector

Scans URL in real-time

[embed]http://app.webinspector.com/online_scan[/embed]

UrlVoid

Scan websites with multiple website reputation engines to check if the website is safe and legit.

[embed]http://www.urlvoid.com/[/embed]

IpVoid

Scans an IP address using multiple DNS-based blacklists to facilitate the detection of IP addresses involved in spamming activities.

[embed]http://www.ipvoid.com/[/embed]

VirusTotal

Free service that analyzes suspicious files and URLs and facilitates the quick detection of viruses, worms, trojans, and all kinds of malware.

[embed]https://www.virustotal.com/[/embed]