Free resources such as icons, pattern, UI kits, layouts, etc. for Website Designer is available in abundant quantities. But not everything you find can be used for free, especially for commercial projects. You have to understand each license granted from its creator. Most of these resources are to be used for personal (as a reference) and non-commercial projects such as charity website or personal blog. But there are some UI Designer and Web Designer who humbly shared their resources for free without any frills to include a link to their copyright. Here is 15+ Awesome & Detailed Icon-sets that you can use for free for personal and commercial projects.
15+ Totally Awesome & Detailed (Yet Free) Icon-sets
The Ultimate Free Web Designer’s Icon Set via SmashingMagazine
Total: 750 icons at 48x48px
Format: PNG and PSD
Designer: Oliver Twardowski
Aroma (250+ PNG Icons) via SmashingMagazine
Total: 250+ icons at 24x24px
Format: PNG
Designer: Oliver Twardowski
Professional E-Commerce Icons Set (20 Icons) via SmashingMagazine
Total: 20 icons at 64x64px
Format: PNG
Designer: Web Icons Set
Free Medical Icons Set (60 Icons) via SmashingMagazine
Total: 60 icons at 32x32px and 128x128px
Format: PNG
Designer: Centigrade
Web Injection Free Icon Pack via MidtoneDesign
Total: 26 icons at 48x48px
Format: PNG
Designer: Jonatan Castro Fernández
32px mania via MidtoneDesign
Total: 179 icons at 32x32px
Format: PNG
Designer: Jonatan Castro Fernández
Basal Icons via DesignKindle
Total: 50 icons at 32x32px
Format: PNG and PSD
Designer: Tomas Bartko
Build Icons via DesignKindle
Total: 50 icons at 48x48px
Format: PNG
Designer: Umar Irshad
Mush Icons via DesignKindle
Total: 10 icons at 32x32px
Format: PNG and PSD
Designer: Pranav Pramod
Koloria: Free Icons Set via GraphicRating
Total: 160+ icons at 32x32px
Format: PNG
Designer: Graphic Rating
Onebit free icon set #4 via Icojam
Total: 32 icons at 48x48px
Format: PNG
Designer: Ico Jam/Stan Khodjaev
Free Pixelbox icon sets via Icojam
Total: 424 icons at 16x16px
Format: PNG, BMP, GIF, ICO, ICNS
Designer: Ico Jam/Stan Khodjaev
WooFunction Amazing Web Design Icons via WooThemes
Total: 178 icons at 32x32px
Format: PNG
Designer: Liam McKay
Ikonos Icons set via kiko11
Total: 28 icons at 32x32xpx
Format: PNG
Designer: Yoni Lopez
Trainee Icons Set via emey87
Total: 226 icons at 32x32px
Format: PNG and PSD
Designer: Manuel López
iCandies Icon Set SmashingMagazine
Total: 60 icons at 32x32px, 48x48px, and 64x64px
Format: PNG
Designer: Icon Eden
Of all the above icon license states that you can use all collection as personal or commercial projects. If you have other collections, please share in the comments field.