Finding a VPN provider is the easy part (e.g., StrongVPN). The problem is that your Linksys doesn't support a VPN client. The only way to correct that would be install dd-wrt (third party firmware), which would add that capability.
For most ppl, however, I’d recommend getting a separate dd-wrt router, configure its WAN w/ PPTP (the most common VPN client), and patch it to your Linksys e3000, LAN to WAN.
[e3000](lan)<-- wire -->(wan - pptp)[dd-wrt - vpn client]<-- wire/wireless -->[ht-e5500]
Now you can decide whether or not you use the VPN for any given device(s) by merely the choice of router, wired or wireless.
You may be able to find other off-the-shelf routers w/ similar capabilities, but I know dd-wrt works well in this regard.
Another quick-n-dirty option would be to use a laptop (a desktop would work too, it’s probably just not as convenient), configure it as a PPTP VPN client (it’s built into all versions of Windows) on the wireless connection, connect the wired port of the laptop to your device (or devices if you use a switch), and bridge the wireless and wired connections. In effect, you’re using the laptop to create your own router w/ VPN client (ala dd-wrt).
[e3000]<-- wireless -->[laptop – vpn client]<-- wire -->[switch - optional]<-- wire -->[ht-e5500]
You'd also have to make sure the Windows VPN client was configured as your default gateway (it’s an option in the VPN client configuration).