Being as shy as I am, I would mostly lurk at these sites/blogs, rather than participate directly. But still, just reading the posts made me feel less alone in my experience.
There's a wonderful page at Absolute Writes (entitled "Rejection and Dejection," lol) that contains dozens of threads, each with a similar purpose--chatting with other writers who are in the holding pattern--waiting, waiting, waiting to hear something either from an agent or editor. Or, who are tired of the rejections and need a little morale boost.
Inevitably, amongst the frustrated posts, there are always success stories that inspire the rest of us. They offer us something tangible, something to hope for, a reminder that sometimes, a publishing story does have a happy ending.
I also love that there are different "levels" of waiting-hell/waiting-purgatory (the Dante-inspired titles are so creative) on that board -- those who are waiting on agents, those who are waiting on editors, even those who just got a book deal and have no idea what to expect next. All can commiserate and swap war stories and pat each other on the back. (Cyber chocolates and spirits are usually offered along with said pat on the back!). The camaraderie at AW, most especially on that "Rejections" page, is downright inspiring.
It's easy to feel alone in the writing process, especially if few or none of your friends/family are writers. So, if you're feeling alone in your experience, just skim through any one of those threads, and you'll feel instantly better (or, at least, understood).