My colleague Ryan just posted about a simple method to increase the height of picklist dropdowns in the SalesLogix web client.
I have a slightly different way to accomplish the same thing for individual picklists, so while not really more difficult to do, would require you to do it for as many picklists you want to modify. Ryan's solution modifies a stylesheet to affect all picklists in the system at once.
In order to alter a specific picklist on a quickform, add a new C# Snippet action item to the Load event of the form, and add the following code to the action item:
string script = "var btn = document.getElementById('" + pklType.ClientID +"_Items'); if(btn) btn.size='8';";
ScriptManager.RegisterStartupScript(Page, GetType(), "FXSetPickListSize", script, true);
This particular code sample will modify the Account Type picklist on the AccountDetails quickform to a height of eight lines. Make sure you set the On Repaint Event and Refresh Data properties to True for the C# Code snippet, otherwise the change will not persist.
If you want to see how to do this for all picklists at once, see Ryan's post here.