Dreamcolor

You can write a simple post in frontend without login to backend. 
You can easily to post something like Twitter. Write Sideblog is also good idea.

Quick Press Widget

You can write a simple post in frontend without login to backend.

Sven Lehnert

gfirem

Themekraft

BuddyForms

konradS

Camilo

This add-on lets you render ACF field groups inside BuddyForms so users can create and edit content from the frontend—while keeping ACF-powered meta in sync.
Highlights 
– Works with ACF Free and PRO (ACF must be installed separately). 
– Map ACF field groups to BuddyForms forms for frontend create/edit. 
– Supports common ACF field types (text, textarea, select, checkbox, date, color, maps, etc.). 
– BuddyForms Moderation support for review/approval workflows. 
– BuddyPress integration: sync selected ACF fields with xProfile.
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Note: This plugin integrates with Advanced Custom Fields; it does not bundle any ACF code or assets.
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BuddyForms Advanced Custom Fields

Add BuddyForms frontend forms that map to field groups created with the Advanced Custom Fields plugin. Independent integration; ACF is not included.

Quick Press Widget vs BuddyForms Advanced Custom Fields