Creating user-friendly forms, login screen, and search boxes is an important bit of design. Whether you just want to make your forms a bit more aesthetically pleasing or if you want to increase usability by changing the appearance of standard forms, the resources below can help.

Create Custom Search Bars with Image Replacement using CSS
The incorporation of custom elements, like search boxes, can set your website apart from its competitors. This tutorial covers how to add a custom search bar to your site, though it’s not cross-browser compatible.

Fancy Form Design Using CSS
This article covers form styling with CSS.

Designing The Search Submit Button – A CSS Cross-Browser Compatible Solution
Learn how to create a custom image like a magnifying glass, or the word ‘GO’ in a circle, instead of the default search submit button.

Making Forms Convert Through Awesome Inline Labels
This tutorial shows how to increase form follow-through by using better inline labels.

CSSG Collections: Web Forms
This is a collection of uniquely designed web forms available to use for free.

45+ Really Essential Free HTML [Form] Enhancements
This collection of free form enhancements covers a number of CSS techniques.

minimal form layout/quick css tricks
This post gives some quick CSS tricks for minimalist form layout and design.