How to efficiently identify Lego bricks and find their names? I've found http://rebrickable.com/myparts linked in one of the answers here on this site and I'd like to list all of the parts I have at home (probably a thousand or two). The problem is, there is a lot of similar pieces on Rebrickable, including some which have "similar" in the thumbnail image, or have three zeros for parts, sets and colors.

For example there is a 1x2 brick with no hole in it: 3004. What is the difference between this and 3004px3? Can I filter the useless bricks out? How can I find the version with circular hole in the middle used a lot in Technic?

But the whole question boils down to: How to efficiently identify bricks and their names?
In my experience, the Bricklink catalog is the most complete parts list. It is organized in fairly logical tree by part type (brick, plate, wheels, slope, etc). Once you get familiar with it, you should be able to identify parts fairly quickly.

If you take a look at the 2 parts that you mentioned in your example on Bricklink, you can clearly see the difference between them:

3004:



3004px3: