Update (26 Jul 2018)
Minor update to prevent the two parts from overlapping.

Update (4 Oct 2017)
The "Swap_Catches" option now affects which piece is considered the vertical piece for the "Dual_Vertical" option. This can be useful for those who need to mount the holder horizontally, and at the same time avoid blocking the charging port.

Older versions are available as a zip files.

Update (31 Jul 2017)
Added a "Swap_Catches" option. When set to true, this swaps the catches on the vertical and horizontal piece. The vertical piece will have the "hook" catch, while the horizontal piece will have the straight catch. This is useful if you need to mount the holder on a horizontal bar, or if you wish to mount your phone horizontally.

If you want the original version, both v1 and v2 are available as a zip files.

Update (11 Jul 2016)
Added a "Dual_Vertical" option. When set to true, this allows you to attach two vertical pieces instead of one. This can be useful if you want to charge your phone while it's in the holder.

Added a "Grip" option. This allows you to increase/reduce the height of the top catch, trading off grip tightness to ease of insertion.

Few other minor changes. If you want the original version, it's available as a zip file.

Update (22 May 2016)
Added a vertical offset option when using the Customizer. The original design always places the side grip right at the middle, and this can obstruct or press on the side buttons for some phones. The vertical offset option solves this problem by shifting the phone up or down to avoid the side buttons.

Update (15 Jun 2015)
Added an OpenSCAD version that can be customized to your phone and bike. There are also a couple minor changes to reduce obstruction to the screen and home button.

This replaces my earlier phone holder (http://www.thingiverse.com/thing:611691), and allows a phone to be mounted on the handle bar of a bicycle (...tested with a Cannondale F7, ymmv).

I've included versions for...

HTC M8
HTC ONE
iPhone 4 and 4S
iPhone 5 and 5S
iPhone 5C
iPhone 6
LG F5 (Tested)
LG G2
LG G
Nexus 4
Nexus 5
Nexus 6
Samsung S3
Samsung S4
Samsung S5
Sony Z1
Sony Z2
Sony Z3
Xiaomi Mi2
Xiaomi Mi3

...mainly using dimensions from Wikipedia. Most of these are untested, so do let me know if it works for your phone!

This was inspired by Biel's design (http://www.thingiverse.com/thing:176132), but is not a remix. Compared to the other phone holder designs on Thingiverse, this one is meant to be ultra light (8 grams) and easy to print (zero bridges or overhangs, and prints in well under an hour), while still holding the phone pretty firmly (...yet to test this fully, but I'll update on the result the next time I hit a bus).

You'll need a couple of zip ties to secure this to your bike.

Designed in FreeCAD (fcstd file is included) (OpenSCAD version added) and printed in ABS using Cura. Should work great with PETG. PLA may be too brittle, but some makers have reported success.

It is strongly recommended to use the customizer version (...click "Open in Customizer"), but the original STL files are still available for those who wants them. The following instructions are for the older STL version:

The STL file contains 2 parts, and you'll have to split them up and lay them flat before printing (...in Slic3r, right click and select "Split".).

It should not be hard modifying this to fit your phone model using FreeCAD, but be warned that FreeCAD (...at least for the version 0.14 that I'm using) seems to have trouble making up its mind and may complain about redundant constraints when the dimensions are changed.