What platform are you using?

You can use something like "nbtscan" if you have netbios enabled, but output to CSV. Then import to spread sheet and sort by the MAC address fields. Then compare it to the manufacturer list of the NIC.

Get a list of manufacturers @ http://standards.ieee.org/regauth/oui/oui.txt

The first 24bits of the 48bit MAC will be the manufacturer code.

Example: 00-03-47-xx-xx-xx
Then compare it to the list... in this case it is made by. Intel Corporation

Linksys would be something like:
00-04-5A (hex) The Linksys Group, Inc.
00045A (base 16) The Linksys Group, Inc.
17401 Armstrong Ave.
Irvine CA 92614
UNITED STATES

Just remember... there are far more manufacturers than just linksys...
And... linksys does make other products than routers so, you could have more false positives.

Or, you could do a ping scan and then retrieve the MAC addresses using arp -a.

Then compare them.

I'm not sure how big of a cache that arp will keep though.

I'm not aware of any programs that will give you this info across the network.

nmap's OS fingerprinting? But, it won't show up as "linksys"... it'll show up the operating system. Then if you know you only have a couple of linux boxes, then check into those devices a bit more. I know that dlink uses a varient of *nix and pretty sure the linksys does too. Though... I'm not completely positive.

Just a couple of random ideas.