I have seen people dividing sitemaps into seperate pages if there are too many URLs, like 100 per page. Does anyone think this is a good idea, or is it ok if I have one single sitemap with 2000 URLs?
If you are talking about creating HTML sitemaps, I think you should split it across multiple pages. (i.e. limit each page to e.g. 100 links)
Max 50.000 urls per XML sitemap file. If you want all the gory details, I suggest you check my article about website sitemaps. It explains all sitemap types (e.g. text, HTML, RSS, XML etc.), have code examples of them all, and also links to relevant Google, Yahoo etc. pages should you need even more information.
if your sitemap.xml contains too much URLs and is a big file than you can zip it with wingz. wingz is a free software and easy to use. just delete sitemap.xml and put sitemap.gz to root directory
And you can use robots.txt to restrict some of your pages, because robots.txt is read before sitemap.xml or sitemap.xml.gz. The first line of robots.txt is Sitemap: yoursitemap.xml.