I've said it before and I'll say it again (because Paras and his team deserve it): I tell people about VWO as the prime (and possibly, the only) example of an Indian startup with a truly global product.
Kayako, FusionCharts, BrowserStack, FreshDesk are other great Indian software companies that I admire. (The first 3 are bootstrapped too, as far as I know).
Edit: Sorry, forgot Zoho.