One real easy way is to use
unzip on the command line.
1) If the ZIP file doesn't contain any folder hierarchy, simply files at the "root" level of the compressed file, do this:
- open Terminal and
cd to the folder with the ZIP file
-> The files are extracted directly into that folder.
2) If the ZIP file does contain a folder hierarchy, but you still want to extract everything in the same folder (usually not a good idea, as the hierarchy is there probably for a reason), do the same thing as above, but with
-j modifier for unzip, which means "junk paths (do not make directories)":
unzip -j zipfile.zip
Edit: the same approach works for RAR files, except you'd need to install the command-line unrar tool yourself (unlike with unzip), and I'm not sure what the equivalent for unzip's -j modifier is.