US Consumer Product Safety Commission's database for recalls and product safety alerts
This is a searchable database, and you can also sign up for their RSS feeds. They have it set up so that you can get the feed for all recalls, or just the category(ies) that you are interested in.
This is a direct link to the CPSC infant/child product recalls.
HealthyStuff.org also has a searchable database of recalled items. The database is searchable by brand or type of item, and is particularly useful for looking up many items at once (after a birthday party, baby shower, etc.). Categories include: Toys, Children's Items, Pet Products, Cars, Apparel and Accessories.
Recalls.gov is yet another database. This one has a broader range of categories; Consumer Products, Motor Vehicles, Boats, Food, Medicine, Cosmetics, Environmental Products.You can sign up for email alerts, and report dangerous products.
Skin Deep Database. I use this one often. The Skin Deep Database is a guide to cosmetics and personal care products. The have thousands of entries which are rated by the safety of their ingredients. They recently put out a sunscreen guide that is fantastic. I've gotten into the habit of checking the database whenever we are thinking about trying a new product, and I feel like it's such a quick and easy way to help us eliminate as many toxins from our home as possible. The Skin Deep site is an offshoot of the Environmental Working Group webpage (another great informational site).
Another favorite of mine is ZRecommends. This blog is written by parents who are passionate about the safety of the products that they bring into their home (although it's turned into a lot more). They do green kid's product reviews, and write amazing product guides for almost every baby item out there. More recently they have started to research other household items as well.
The Soft Landing Blog was one of the first sites that I found when I started researching safer plastics and it is still one of the sites that I visit regularly. They also have some great product guides, and work hard to bring their readers the information that they need to make informed decisions. They also have an online retail shop where they only stock the safest kid's gear.
SafeMama is an all-purpose eco-kid (and mama) product safety site. With reviews, recall notices, and cheat-sheets, it's a great resource. Not just toys and diaper cream, they also highlight news issues of importance to families striving to make safer choices.
Here are a few of the retail sites that I trust to have high safety standards. I feel like they take the time to research the quality of the items they sell/make, as well as have great customer service.
The Soft Landing Thoroughly researched products,extremely high standards.
Earth Mama Angel Baby has wonderful skincare products for mamas, babies, and mamas-to-be
ReusableBags.com I've gotten many of my reusables here (disclaimer: I am a Reuseit.com ambassador, but this endorsement is my own, unsolicited opinion. I shopped there long before becoming an ambassador.)
And, just because I think it's important to know what you are eating,
FDA Food Safety Recalls RSS feed / FDA Food Safety Press Release database
Feel free to add your favorite sites in the comments!!