Yes, I've had visits from my Bridgekids Sinbad and Tiger, and a lot of the people I've met while a moderator at Petloss.com (2003-2006) and now as admin of the Lighthouse, another grief support site, have had similar visits from their pets who have crossed over. Sometimes they're called signs and visits, but they're also called ADCs or after death communications.
Scott Smith's book The Soul of Your Pet
is a wonderful book about these communications.
I'd also recommend two websites about ADCs.
The first ishttp://www.after-death.com/
the website set up by the authors of Hello from Heaven
, a wonderful book on ADCs. If you check their message boardhttp://www.after-death.com/mb/main.shtml
you'll often find messages about ADCs from pets. (There don't seem to be any threads about ADCs from pets there right now, which is unusual; I'd check again in a day or two.)
The other site is the After Death Communication Research Foundation website athttp://www.adcrf.org/
They often have accounts of ADCs from pets, and if you use their Search you can find some of them in their archives.
These sorts of experiences are very comforting. There were always lots of posts about them at Petloss, so when we created the Lighthouse last year I set up a two-category forum just to discuss ADCs, one forum to talk about what they are and how to make them more likely (most experts on ADCs recommend meditation), the other for people to post their own ADC stories. There are a hundred topics in the ADC Stories forum now, and I know those aren't all the ADCs posted on the board, that some are mentioned in other forums.
This page on the After-death.com sitehttp://www.after-death.com/about/adc.htm
has some wonderful info on the types of ADCs, which really don't differ that much from human to pets' spirits. It helps to have some idea what to watch for.
And this page from that sitehttp://www.after-death.com/about/billg.htm
has some tips on how to make ADCs more likely.
I'm so sorry you lost Sassy and Tabby, but I'm glad you've had visits from them.