Yes, you can if your income is low enough and your assets are limited. The maximum federal benefit for SSI is $637 a month for a single person and $956 for a couple. The maximum an individual can earn is $637 a month (maybe a bit highr for 2010) and for a couple it's $956. Assets can't exceed $2,000 for a single person and $3,000 for a couple. Exceed either income or assets and you are not eligible.
Some states (like CA) give SSI recipients additional allotment.
Hope this helps.
Trudi