I was reformatting logos for a conference's sponsors web page, and a google search on how to standardize logos for visual consistency turned up nothing. So here's how to achieve a clear, consistent sponsors page with logos. (Basic rule: equalize and align logotypes).

1. Set maximum vertical size: 100 pixels is a good default
2. Resize logotype (the company name text) to be 1/5th of max vertical size: in this case 20px: adjust as appropriate to your logo set. Approximations work, and are not easily visible. This is the single most important step in providing consistency. In case of logos with sub-text or taglines, design for the company name.
3. Align logotype to central 1/5th of logo area: or whatever fraction you used in step 2.
4. Desaturate: do this and the next step if you're trying to standardize colors to fit into your website theme.
5. Adjust brightness/contrast to an apropriate grey/black/white: never tint to anything other color. You may have variations if you have logos with multiple brightness components.

This approach works best when you have a lot of different logos that aren't combined into one image (for display).