Based on an excellent suggestion, I'm going to clean up the rooted threads here at the top by creating some links below that you can go to for quick reference. Lots of good information for the new and old engi alike!
Engineer Guide MkIII - not the best, but the starting point for every engineer.
Pet Related Questions
Engi Pet Attack Ratings. More up to date,
Engi pet HP and NP: RK Pets & SL Pets
Endgame pet stats
Effects of agg/def and other trimmers
Tradeskilling
Pricing for Tradeskills 3.0
Tradeskill Items and where to get them
Tradeskill Maximum Needed
Tradeskill Maximum Possible
Top Craft with low IP cost Guide
Commanderb's Guide to alien armor Creation
Muha's guide to Implant Design and Construction
Nemezyda's Implants Assembling Guide
Tradeskill websites
AOcrafter
Help with creating scripts for offering tradeskill services
Build Guides
HugeNick's guide to Multi-Purpose Engineer
Ultimate/Consolidated Engineer breed choice guide
Keyley's Guide to MA engineer MK 2
Mid-High Level Twinking
Muha's symb twinking "guides": 210 symbs before 170, 220 symbs before 180, Twinking for 205, 210, 215, 220 (including 2xPeregrines Mk6)
Silverado's Little DD Guide
Miscellanea
Gearbox and Bob Comics
BotEng - Profession Chat Channel
Guide to Engineers in society
250+ Symbiant Camping
Takun's Control Unit Symbiant Guide
Engineer' perklines overview
Thread on Current Balance issues 1/13/10