There are a few apps that can help you in your ideation  process, especially when you are doing asynchronous or remote ideation sessions or you are prioritizing and filtering ideas after a idea generation session. Here a few:

1. Scrumblr (free — web)

2. Candor (free — web)

3. Miro (freemium — web, Mac, Windows, iOS & Android)

4. Stormboard (freemium — web)

5. Wonder (freemium — web)

6. viima (freemium — web)