I finally converted from .bmp, which I grew accustomed to before I knew there were different image file types, to .png. I can't tell the difference in quality, and the improvement in file size really is drastic.

From what I know (limited knowledge, based on Wikipedia reading mostly ;) ), BMP is a straight format : no compression, and each pixel is stored in a few bytes. PNG on the other hand, is compressed, but losslessly, meaning you don't lose any data by converting BMP to PNG, and so when you convert the file back to BMP it's supposed to be identical to the source. PNG is some kind of special zip format for images, just like FLAC is for sounds. Furthermore, PNG is a free format, you can use it as you want. The downside of it is that PNG files are much heavier than JPG files, which are compressed with loss of data and thus are of lesser quality. As for the comparison with GIF files, except for animations (for which there are PNG-extended formats), PNG is supposed to be much superior to GIF almost anytime.

jpg for photos
gif for animations
bmp for laughs
png for everything else

jpg for photos
gif for animations
bmp for laughs
png for everything else

Very close, but I would add svg for diagrams. Ever major browser supports it now, and vector graphics scale and compress very well.

The biggest thing is to use jpg only for photos. It's good at that, and bad at just about everything else, even though people use it for everything.

I use .tiff for when I scan things in high-res, otherwise its minimally compressed jpegs.

I miss .pcx

.png the great majority of the time
.psd when I'm working on something in Photoshop with lots of layers which I need to save as it is now
.gif for animations

and...

.pcx only for modding Civ3 :D

I like the compression you can acheive with PNG, with no loss of quality, you could think of it as a bmp in a zip.

I like the compression you can acheive with PNG, with no loss of quality, you could think of it as a bmp in a zip.

Especially if you use it in conjunction with something like PNGOUT; the file sizes can be quite small.

.png are the type I save things as most frequently, so I'll vote that.