Update: The site has returned in its same old, hindered form.
The web site to perform online ESN swaps for Sprint PCS lines, activate.sprintpcs.com has been offline for approximately a week now. The site’s functionality has been less and less useful as time has passed, due to the site’s inability to work with any line that has a Vision phone on it, and the inability to activate any PDA/Phone device.
With Sprint customer service hold times reaching new highs for the year, it looks like Sprint may finally be rebuilding this tool. Verizon offers a similar service for their customers, and does not have such restrictions on what devices can be activated.