A few days ago I found a new favorite resource when doing mockups. Often enough you need a placeholder image just to occupy some space while positioning elements and not necessarily when showing clients (don’t use these placeholders for that).
Placehold.it is a service that generates nice and tidy placeholder images on the fly (which can be formatted too if you like). By just using the format and their domain as your image URL, you get a nice-looking placeholder, much better than a blank image tag.
I found this last week over on Smashing Magazine. They have a freebie design resource called the Facebook Fan Page GUI PSD. Basically, it is a layered Photoshop document containing all the Facebook user interface elements that makes it easy for you to design graphics for either Facebook walls or tabs.
What makes this helpful is that you get to design your graphic while seeing right away how it looks on Facebook’s design. What’s more, they are promising that with every change to the Facebook UI, this file will be reproduced 24 hours later.
I am a big fan of templates that gives me just a good-enough start to be helpful, yet little enough to be over the top. When moving to HTML5 coding, the HTML5 Boilerplate package might offer you a good start on what you want and need for your project.