If you aren't buying in bulk already, then you are likely accumulating a ton of packaging from the modern food industry. One of my favorite repurposing tips is to take the jars that salsa comes in, wash them out, and use for organizational purposes, Mason style jars make great cups as well!
This may be obvious to people, but if you do a lot of mailing, particularly for gifts, you should always seek to repurpose the boxes you receive to save on packaging! Then you can use newspaper or mailing to ensure the package is tightly packed and the contents safe inside! While I like to send gifts electronically to avoid the damage of shipping cross country via a courier, sometimes you need to send your homemade gifts to your cousin in Los Angeles!
If you ever purchased CD's in bulk to create your own playlists, repurpose the empty container into a bagel sandwich holder! Obviously not practical for everyone, but it looks great.
Paperclips are great for wire organization rather than purchasing some plastic doo-hicky.
Repurpose old books as shelves, for a cool antique look
I use broken clay pots as garden markers rather than purchasing some sort of cardboard marker that sticks in the ground. Aesthetically they are much more pleasing, and it gives new life to your chipped pots!