If you're like me an often find yourself trying to research that new piece of gear, finding online reviews is probably the single most important factor in your decision making...at least until you get a chance to try said item out yourself. That said, finding decent places can be a pain in the ass since Google results are flooded with dubious customer review sites that are of little to no help. To help you wade through the web's cesspool of reviews, here a bit of a compendium of what's out there:
DPReview - A common first stop for body reviews, plus a limited number of lens reviews.
The-Digital-Picture - Canon and for-Canon equipment only (bodies, lenses, lighting, accessories). Includes a very useful lens comparison tool. Reviews are heaving based on comparisons to similar products.
Photozone - Lens reviews for virtually all popular digital formats and systems. Don't get hung up on star ratings, read what they actually write.
Cameralabs - Fairly extensive set of body and lens reviews, of all major brands as well.
Lenstip - Lens reviews for all brands, and some occasional broken English to contend with.
DxOMark - Quantitative reviews of lenses and sensors; a point of much contention on forums.
Bob Atkins - Almost entirely Canon equipment, his reviews are partially CC'd to photo.net.
Peter Kun Frary - Canon lens and body reviews. Includes many discontinued EF lenses that lack reviews elsewhere. Written from the perspective of a landscape/portrait shooter.
Steve's Digicams - Possibly started by a guy name Steve. I'll investigate further.
Thom Hogan/Sansmirror - Nikon and mirrorless system reviews, plus editorials on the industry. The Nikon equivalent of Bryan from TDP.
Canon Rumours - Recently started doing reviews, starting with more expensive L gear.
DC Resource - Recently ceased updates, but still has an extensive back-catalogue.
Mir - Not reviews per se, but a wealth of info on a lot of less common and ancient gear.
Fred Miranda - User reviews and aggregate lens data.
SLR Gear - Nearly identical to Fred Miranda, but includes an official review for most lenses.
Imaging-Resource - Similar to Cameralabs.
Ken Rockwell - Get a bag of road salt before reading, you'll be needing plenty of grains.
Steve Huff - Good for those who are insistent on getting 'real world' reviews.
Digital Rev - Video reviews of pretty much everything. Kai is basically the Napolean Dynamite of the photography world: he's either your favourite or most hated reviewer.
Speedlights.net - Reviews of lighting equipment for Canon and Nikon Systems.
Flashhavoc - More lighting equipment reviews.
Of course there are other sites out there that contain reviews, I just can't/won't name them all. These should be enough to get your research started Also, as a general rule I'd avoid any of those consumer reports type reviews, since those are typically done by people with little product knowledge and rarely take anything other than value for money into account. Anyway, happy hunting and good luck.