Check out:
http://wiki.project1999.com/Guilds:Guild_List. At your level you'll mainly want to look at the "Casual Guilds".
Once you find some guilds that seem promising, follow their forum link or website link to learn more. The wiki is best for getting the overview of all options, but because it's a wiki and not a primary source (like the forum thread/website) it's can be less up to date than those primary sources.
As for raiding, there's only a small overlap between guilds that take <45 characters and guilds that raid. Most raid guilds require 45+ because you can't enter the planes until then, so many people join casual/family guilds to level up then later switch to raid guilds.
If you want a single guild for both I think you'll mainly want to look at Dawn Believers and guilds that are members of the AEGIS alliance (which are mostly under the "raid guilds" category, but a few of those do accept lower level members).
Hope that helps.