- Protocols (BGP,EIGRP, First Hop Redundancy, IEEE 802.11 WLAN, IEEE 802.1X, IPsec, IPv4 Multicast, IPv6, IS-IS, OSPF, Spanning Tree)
- Applications (tcpdump,Wireshark display filters)
- Reference (IOS IPv4 Access Lists, IPv4 Subnetting, Common Ports)
- Syntax (Markdown, MediaWiki)
- Technologies (Frame Mode MPLS, QoS, VLANs)
- Miscellaneous (Cisco IOS Versions, Physical terminations)
Courtesy of PacketLife.net
I had put together a small Cheat Sheet for MySQL a couple of years back which helped me in remembering the command line parameters used in manipulating MySQL database.
The idea of a cheat sheet is to help a person keep track of all the essentials of a topic. Thus cheat sheets play an invaluable role in brushing up ones knowledge in the least possible time.