I like to highlight content from smaller sites, and have linked in the past to theunlockr.com, which is run by David Cogen. The site has several videos related to "rooting" or hacking the Nook Color with custom firmware that allows you to turn Barnes & Noble's color e-reader into a full-on Android tablet.
Cogen recently put together a video comparing a Nook Color rooted with a Froyo (Android 2.2) hack with a Samsung Galaxy Tab that has very similar specs but includes front-and-back facing cameras and a 3G data option for those who want to pay the added service fees. The Galaxy Tab has a smaller footprint, whereas the Nook Color is slightly thinner.
If you're willing to opt-in to a two-year contract with a carrier (the Tab comes in Sprint, T-Mobile, AT&T, Verizon, and U.S. Cellular versions), you can get the Tab for as low as $250. But the unsubsidized version costs $500, which is twice the price of the Nook Color. When Samsung releases a $399 Wi-Fi-only Tab--it's coming soon--that will narrow the difference to $150.
In his video, Cogen points out that the rooted Nook Color isn't as stable as the Galaxy Tab (although the custom firmware continues to improve with each new release), but otherwise the two devices seem to perform pretty similarly. Some people will always prefer "official," company-backed products to so-called hacks (rooting the Nook does void your warranty), but the price delta here makes for an awfully compelling case to go the root route.