If you want to purchase Russian antiques, be prepared. Know what you are looking for and what it will take to get it back to your home country. For some large or more costly items, they may be best purchased from shops elsewhere (never trust valuable items to the Russian postal system). The following Russian antiques shops on the web are meant as resources--I personally cannot vouch for their reputability. In some cases, you may be able to order Russian antiques; again, I cannot advocate this.
A La Vieille Russie specializes in high-end antique items and jewelry. They have a section dedicated to Faberge items, like enamel frames, egg pendants, and other decorative items. The ALVR web catalog is great for browsing (and great for dreaming). An old family-run business, they are located on Fifth Avenue in New York City.
A family-run business too, S. J. Phillips is another high-end antique dealer. Their online catalog is a smorgasbord of treasures, many of them with Russian provenance. Many celebrities shop at their New Bond Street, London location.
An exclusively high-end Russian antiques dealer online. The website states that there is an unconditional guarantee for the authenticity of the items. Beautiful pictures detail appropriate hallmarks and prices are clearly posted. Some Faberge items as well as Imperial goods. A good site for browsing or for research.
Located near Melbourne, Australia, Roy's has a special section devoted to Russian antique ceramics, enamel, silver, and icons that predate 1850. Excellent selection of Russian enamel pieces. You may come across similar items in Russian antiqus markets, so Roy's is great as a price comparison resource.
With rather vague dates for porcelain and silver pieces, this site is best used as a launch point for further research into the area of Russian antiques. The hallmarks are not visually documented on the site itself, and the lack of detail in the descriptions of the item is rather disappointing.
Russian antique curiosities, from Christmas ornaments to space exploration memorabilia, fill the pages of Motka.com. Rather reasonable prices mean that authenticity isn't such a large concern as it is with "Faberge" objects d'art. This is a fun site for those just becoming interested in Russian antiques.
A good selection of Russian coins, medals, and military items, Russian Antiques also features some contemporary objects. Many of the items are from the 20th century, so this site is perfect for the collector of Soviet-era memorabilia.
If you can get past the rather amateurish layout of the site, you'll find the descriptions of the featured Russian antiques to be full of valuable information. The visual and text descriptions of hallmarks are useful for familiarizing yourself with what can be the most important part of the piece.