A relatively recent anime series, shown on the Cartoon Network at one time, and for some strange reason, shown during Cartoon Network's Toonami block for part of that time.

Based on a series of children's books by Japanese author Ritsuko Kawai, Hamtaro (or "Totokko Hamutaro", as it's called in Japan*) features the adventures of the title character, an adventurous, amiable, and kawaii little hamster named Hamtaro. Hamtaro's owner, fifth grader Laura, just moved with her family to a new neighborhood, and is eager to make new friends. So is Hamtaro. Of course, since Hamtaro is the main character, the action mainly focuses on the exploits of him and his buddies in the "Ham-Ham Friends", a club for pet hamsters living in Hamtaro's neighborhood, who meet while their owners are away at school or otherwise out of the house. Members include (note that the name in parentheses is the original Japanese name):

Boss (Taisho): A feral field hamster who lives in an elaborate burrow converted, Rescue Rangers-style, into a fancy clubhouse for his friends. The "gruff loner who's really a nice guy on the inside".
Oxnard (Koushi): A large, mottled gray hamster with a big appetite for sunflower seeds. Rather dim, but loveable. His owner is Laura's best friend, Kana. Not coincidentally, he's one of Hamtaro's closer friends.
Bijou (Ribbon): "A recent resident of France", according to the official website, and this is reflected in her obvious French accent. Bijou is a soft-spoken sweetheart whose looks have charmed many a male hamster. Boss has a bit of a crush on her, but I think her affections lie with Hamtaro.
Howdy (Maido): An endearing goofball with a ridiculous Texan accent, he lives in a convenience store. He's a hard worker, but he does have a well-developed sense of humor. At least, he likes to think he does. In fact, he's often the only one who laughs at his jokes.
Dexter (Megane): A gentlemanly hamster with an odd glasses-like marking on his face and a little red bow tie, Dexter is in fact a bit of a know-it-all who likes to give his friends advice, whether they asked for it or not.
Snoozer (Neteru): A borderline narcoleptic hamster who lives with Boss. Spends most of the time sleeping (practically all of it, in fact o_O), but suprisingly enough, acts as a font of advice by the expedient of talking in his sleep.
Pashmina (Mafura): She may seem flaky, what with her obsession with her favorite pink scarf which she always wears, but she's actually quite dependable. Dexter and Howdy are always squabbling for her affections. She looks after the youngest member of the Ham-Ham Friends:
Penelope (Chibimaru): A small yellow hamster who's a bit exciteable, and clings to Pashmina all the time. The only sounds she seems able to make for much of the series is "ookyoo!" (though she eventually switches to "oopwee!")
Panda (Panda): Very clever with his hands, Panda's owner's parents are carpenters, and Panda seems to have picked up a few things. He helps build and fix furniture for the clubhouse.
Cappy (Kaburu): A shy, somewhat eccentric character who likes wearing things on his head. Aside from his usual green bandana, he usually wears a saucepan.
Maxwell (Noppo): A hamster who's fairly educated in the ways of the world, and who always carries a little book with a blue cover. His information is usually more practical than Dexter's.
Sandy (Toraham-Chan): A perky, "valley-girl" hamster who's into rythmic gymnastics. A major storyline during the series involved her search for her twin brother:
Stan (Toraham-Kun): A party-loving hamster who usually carries a pair of Maracas, Stan is a bit of a smart aleck. He's into Latin music, and likes to consider himself a ladies man.

Other characters include:
Jingle (Tongari): A somewhat hippy-dippy wandering musician who carries a little guitar strapped to his back. He sounds like a beatnik, and likes to speak in rhyme and talk in riddles. Jingle seems like a bit of a space cadet, but he often acts as an unexpected help for the Ham-Hams.
Pepper (Jajaham): A countrified girl hamster with pigtails, Pepper is the pet of Laura's older cousin, who owns a farm in the country. Pepper is energetic and adventurous, and has an affinity for animals. Oxnard seems to like her in a "platonic boy-girl" way common to childrens' cartoons.
Elder Ham (Chourou-ham): An extremely old, and supposedly wise hamster who gives advice to the Ham-Ham Friends on occasion. He's really a bit senile, and has a tendency to fall asleep in broad daylight, but he means well.
Auntie Viv (Ohamubaasan): The energetic, wacky old aunt you might or might not have had, in the body of a hamster. She blows into town from time to time to have a little fun with the Ham-Hams. Apparently, Viv and Elder Ham were quite an item in their youth. Scary thought, isn't it?

While the characters seem fairly textbook, and the show's visuals are definitely bishoujo and may be too cutesy for some, I rather like the show for it's camp appeal. I also appreciate the limited amount of cheap attempts at covering up references to Japanese culture from the original series, but that's a personal thing.

More info can be gleaned from http://www.hamtaro.com/, including explanations for the various odd, onomatopoeiac noises the hamsters make ("Ham-Ham Words").
*Special thanks to driptray for originally noting the Japanese spelling of the name to me.