Vagrant bundler
Access the bundled gems on your vagrant box from your host.
Floating point arithmetic is going to kill you
We all know that floating point arithmetic is imprecise but most of us pretend this isn't a problem until it reaches out and bites us.
Delete/put links break your Rails app
In Rails you can easily use the link_to helper in your templates to create links that will generate HTTP POST, PUT and DELETE requests when clicked. You can do this using simply setting the :method option, but this ease of use hides a very real problem.
Trigger Integrity builds with a cron job
Out of the box Integrity expects that you will trigger all your builds using Github's post receive hooks, however you can trigger it with cron.
Cucumber screenshot gem
Take screenshots of your web pages with cucumber.
Tuning Mail.app / Gmail IMAP integration
When setting up Mail.app on OS X to access your mail in your Gmail (or Google Apps) account via IMAP it is worth tweaking your 'Mailbox behaviours' and mailbox mappings to make them work together more smoothly.
Ruby docs on OS X with Fluid
Wouldn't it be nice to have a neat little an application on your desktop which allows you to search and view ruby docs.
Install old version of screen using Mac Ports
The latest version of Screen (version 4.0.3 port revision 3) that comes with MacPorts is broken, but you can install an earlier one.