Is there something that will allow me to enter code into an Android tablet and then send it via USB to my Arduino?
No. At the moment the most one can expect is the ability to send/receive data from the Android tablet to control the state of an Arduino. Additionally, a Usb host interface is required on one of the two sides. This is provided by the Arduino ADK, while some tablets may provide it through some special cable or hardware plugin.
I've managed to do it from my nexus 7. See my blog here: Hstam.com is for sale | HugeDomains
The first Android port of the Arduino IDE apparently came out in the last couple days.
ArduinoDroid - see http://arduinodroid.blogspot.com/ for info
mmmm.... it's a big problem
http://www.kickstarter.com/projects/435742530/udoo-android-linux-arduino-in-a-tiny-single-board