Recently new one to add to the list
www.sighost.us
This is definitely a purely sig-hosting service - Semi-strict in initial rules but worth it if you follow them. Main two points to know in advance is that the registration will not accept e-mail address from free e-mail providers (no Hotmail or Yahoo! Mail), so you might want to dig out that POP3 address your ISP gave you if you don't use it often. Secondly, the hostings for two types of pictures - Sigs and avatars. Being caught hosting any other type of image for any other reason is likely to get you kicked off SigHost (possibly with extreme prejudice).
Otherwise, this is a great sig-hosting site to try - Very few members currently (about 500), which means that bandwidth isn't really a problem (they've recently doubled it to what it was a few weeks back). Very short & concise site (no 'paying services' sh*t yet), simple file manager for uploading & managing, forum. Most likely for those who don't need someone to hold their hand in the matter but just want to get the sig hosted.
Is it reliable? Check my sig & avatar for server stability - They're directly on SigHost.us, so if they're down the server is. But I've only ever seen it happen once.
