There is a lot of actions figures featuring Summer Glau as River Tam in Firefly or in Serenity; here's a non-exaustive list of collectibles with references and links.
Pictures from the same collections and more can be found in the gallery : Creativity Section - Action Figures
River Tam - Big Damn Heroes Animated Maquette #1 at Quantum Mechanix
Joss Whedon is known for the post-modern deconstruction of myth: for genre bending that mixes humor, horror, sci-fi and drama to great effect; and for some of the cleverest dialog in entertainment. But above all, Joss is best known for creating babes who kick ass. And no Whedonverse character kicks more ass than River Tam.
QMx has dedicated our first Big Damn Heroes animated maquette to her awesomeness. River is posed in the midst of battle with the Reavers, displaying a dancer's grace with a look (and a copious spattering of her enemies' blood) that shows she means business. Great pains were taken to study both River's prop sword and axe as well as her dress and boots, all of which are re-created in precise detail. Even the uniquely sculpted, highly detailed base evokes the atmosphere of Whedon's Firefly and Serenity Verse, complementing the style and stance of River herself.
Each River Tam maquette is cast in polystone resin and hand painted, reflecting the high standards you've come to expect from a QMx maquette. River measures 6" tall by 6" wide without the base. The base measures 5" x 7" x 1".
The River Tam Big Damn Heroes Animated Maquette is being offered in an edition of 1,500 for just $69.95.
Source : Quantum Mechanix
River Tam - Big Damn Heroes Animated Maquette #5 at Quantum Mechanix
She Can Kill You With Her Brain ...
... but axes are much more fun! She's our brilliant, beautiful, but deadly teenager: River Tam – the psychic savant of Serenity – who kicks butt in hand-to-hand combat and poses a serious danger to just about everyone, including herself.
River is the fifth animated maquette in our best-selling series of Little Damn Heroes™. Standing 4.5 inches tall, our luxuriantly maned, sculpted resin maquette smiles impishly while holding a bloody Reaver axe and sword. All in a day's work for Dr. Tam's little sister.
Before you get lost in her limpid brown eyes, remember that with a firearm, she's a better shot than any of us – with her eyes closed.
Offered in an edition of 1,000, each numbered River animated maquette is priced at just $39.95. Our naughty girl won't be around long, so act fast – and remember to duck!
Source : Quantum Mechanix
River Tam in Serenity PVC Set at Dark Horse
Serenity fans rejoice! The master sculptors at Gentle Giant Studios have taken full-size 3-D digital scans of the main actors from Joss Whedon's blockbuster film Serenity and created a fabulous, realistically detailed PVC set of the favorite three crew members. This process has allowed us to achieve an unprecedented level of accurate detail, both in terms of the distinctive likenesses and the accessories and costumes. Since you can't get these actors to come visit you at home and sit on your bookshelf or computer, this is probably the next best thing!
Featuring Jayne (4" tall), Mal (3.9" tall), and River (3.45" tall), Packaged in deluxe, full-color window box
Source : Dark Horse
River Triumphant Statue at Diamond Select Toys
From the climactic final battle comes this latest Serenity release...the River Triumphant statue! She may be a psychotic killing machine, but River Tam can do some serious damage...especially against an army of Reavers! Standing seven inches tall, this Michael Norman sculpt is in-scale with past action figure releases to create the ultimate Serenity display.
Source : Diamond Select Toys.
Side note : for sold out editions or other prices you can find copies on Amazon