Is it possible somehow to drag and drop image files from a browser or files directly to LyX when creating a latex document? If not, is there any other editor for OS X that can do this? I find it really slow to add images to a latex document, or if you can tell me an easy approach. Thanks
No. It is not possible to drag and drop image files directly into LyX. If you keep all of the graphics that you are going to be using in the document in a single subfolder, it is fairly quick to go through the insert graphics dialog since you don't need to search through multiple directories.
I do not use emacs, but apparently somebody has hacked together a way to automate the process of inserting images into LaTeX documents. This is discussed here: http://lists.gnu.org/archive/html/auctex/2010-12/msg00010.html.
Not by drag & drop, but it is possible with copy & paste. Just put the image in the clipboard and select Edit->Paste Special. LyX will then immediately open a "Save as" dialog, where you can specify where and under which name the image will be saved. However, you can also just press Enter to choose the selected name and path.
Specifically for MacOS there is also the option to Paste as LinkBack PDF, which is enabled if the source application of the image supports the LinkBack technology. Basically, this is what OLE once was for Windows: You can later right-click the pasted image to edit it in the original application. LinkBack is supported by many OS X applications, among them EazyDraw, OmniGraffle, and LaTeXIt.
I think the easiest way to add graphics is to paste them. For example, in a browser right-click and go to copy image. Then go to LyX and go to Edit > Paste Special > Paste as JPEG or Paste as PNG. This also works for me from copying from open office. This works for me using Firefox and Ubuntu with the newest (trunk) LyX version.