Magento is great for e-commerce sites, but it can be difficult to learn. 
Here are a few Magento links I've found useful in my Magento development:
- Richard Castera's Magento snippets Great, simple code for doing things like running an SQL query against the database, getting the current category, and one my most- used ones, adding a product to the cart via querystring.
- Explore Magento Another piece of code I regularly use is gives me the ability to run my own custom code outside of Magento. This can be extremely useful if you have a specialized page not within the main Magento framework. You can find detailed instructions here.
- Magento Database Diagram - Although it's for version 1.16, this diagram is very useful if you want to run your own SQL queries in Magento. It saved me a lot of headache when trying to figure out how to join products, images, and prices for a custom query.
- LoonyBlurb - Custom Layout TemplatesIf you work with Magento for very long, you'll find yourself needing to create custom layout templates. This blog makes that easy to do.
- Finally, my favorite site for Magento snippets: Snippi.net. Unfortunately, it's been down for the past two days--let's hope it's only a temporary setback. If the link works for you, it is the best repository for short, one-line snippets--from doing everything like removing an item from the cart, grabbing a product thumbnail image, or getting session data about a logged-in user.