This is a filament holder with a load cell integrated to weigh the filament spool. I thought this would be a fun way to weigh the filament to ensure I have enough for a print without having to resort to a scale. Assembly BOM, tools required and assembly comments are noted at the bottom.

Summary:
Pros
It works. I've tested it on several prints and the load cell is about +/- 0.05 lbs. This will depend on how well you've calibrated the load cell.

Cons
1) Need help with this... if I power cycle the load sensor PCB which I purchased from Spark Fun, the calibration and tare weight are not saved. I'm not very good with software so I don't know how to change the code which was pre-loaded in the PCB so its saves these settings.
2) Because of this issue, I just never turn it "off".
3) Using a load cell with range closer to the full weight of the filament (typical 2kg) would be better. Load cells like most sensors offers sense errors of some percentage based on full scale. In this case, its a 10 kg load cell. This means the error is a bit higher than say a load cell that's at 4 kg. But as stated, I still get +/- 0.05 lbs so that's good enough for me.

Assembly BOM:
Qty 1: Spark Fun Open Scale (SEN - 13261)
Qty 1: Spark Fun Load Cell 10 kg, Straight Bar (SEN - 13329 ROHS)
Qty 3: McMaster Carr 6389K228
Qty 4: McMaster Carr 2515T180 (Optional if you want the leveling feet)
Qty 2: M5 x 25mm L Socket Cap Head screw
Qty 3: M4 x 16mm L Flat Head Socket Cap Head screw
Qty 4: M3 x 10 mm Pan Head Philips screw
Qty 1: USB to mini-B USB cable

Tools:
M4 Tap
M3 Tap
5/16 - 18 Tap
Wire stripper for 0.8 mm wire (Super fragile, be gentle when stripping back insulation)

Software:
Serial Port Communicator - Options below
1) Arduino IDE serial port communicator
2) Tera Term (This is my preference) Go to this link for a tutorial from Spark Fun. This site will have a link to download.
https://learn.sparkfun.com/tutorials/terminal-basics/tera-term-windows

Assembly Tips:
1) When mounting the load cell, the M4 side of load cell will be on the filament side. You'll see a sticker at the of the load cell with an arrow. Make sure its pointing up, otherwise you get a negative weight reading.
2) Practice cutting insulation back on the load cell wires before cutting to length. Take your time, you can easily cut the conductor along with the insulation.
3) Sorry for making you guys tap threads :(

Using Spark fun load cell:
Go to this site for tutorial on the open scale PCB, very useful.
https://learn.sparkfun.com/tutorials/openscale-applications-and-hookup-guide?_ga=1.116997955.477175760.1487732422

For setting tare weight (Setting weight to be Zero with an empty filament spool), use your most often used empty spool. I'm guessing most filament spools will be pretty close in weight, using your most often used spool ensures you have the best weight info most of the time.

Feed back for improvements are welcome.